A teenage daughter. It wasn't impossible, but Mark was in his early 40s. This was supposed to be his golden womanizing years. But throwing a 16-year-old girl in the mix wasn't going to help. Samantha Riley. He remembered her. One of his college girlfriends. Well, girlfriend was a strong word. They were friends with benefits, if even that. They were friendly and slept together a few times. It was unspoken, but they knew that whatever their "relationship" was, was purely physical.

Derek, Addison, and Mark looked back at the girl, stunned. Baby Nate, thankfully, was still asleep and by now, he was in the car seat Derek bought. Derek looked at Addison, not knowing what to do or what to say. Addison couldn't help but let out a laugh. Of course, Mark had a teenage kid. It was kind of a miracle one hadn't shown up beforehand. When he saw Addison laugh, Derek also started laughing. And it only made Sloan even more confused.

"I'm sorry, it's not you," Addison said as their laughs subsided.

"It's just…it's not that surprising that Mark has a kid," Addison explained further.

"Yeah, there might be a gaggle of Sloans," Derek joked.

"This isn't funny!" Mark barked back.

"It is a little," Derek chuckled.

"So, what happens now?" Addison cleared her throat. Someone here had to be the adult. Mark was too angry and her husband found the situation a little too funny to do anything about it. At least at this moment.

"I don't know…," Sloan fiddled with her fingers now that she didn't have a baby to distract her fidgeting hands.

"Not that I'm doubting your story, but paternity test," Derek offered. He saw the effort his wife was trying to make. But the fact that neither Mark nor Sloan knew what they were going to do didn't make it easy for Addie.

"I'll grab the supplies," Addison said after a minute of silence from both Mark and Sloan.

Addison did the test while Derek watched Mark and Sloan have a staring contest, of sorts. The baby, thankfully, was fast asleep in his car seat the whole time. Derek and Addison, silently to themselves, hoped baby Nate would always be this good of a sleeper.

"Okay, well, that's it," Addison said as she cleaned up the supplies.

"Now what?" Sloan asked.

"Now, we wait," Addison said.

"For how long?" Sloan sounded a bit annoyed.

"Four to six weeks," Derek answered.

"What do I do until then?" Sloan asked.

"Mark?" Addison looked over at Mark, who was still staring curiously at the girl.

"I need a minute." Mark got up for a breather in the hallway.

After handing Addison the car seat with the sleeping baby, Derek followed him outside. When he got there, he found Mark pacing with his hands on his head. Derek thought to say something, but decided it'd be best to give him a minute to freak out.

"You alright?" Derek finally asked.

"I have a kid," Mark said. Saying it out loud didn't help him feel any more relaxed.

"Maybe," Derek warned. They'd just gotten a paternity test done. They wouldn't know for sure for another few weeks.

"No, I have a kid. I'm too old to have a kid," Mark insisted.

"You're not too old to have a kid," Derek couldn't help but chuckle.

"I don't even know how old she is," Mark admitted.

"She's 16," Derek informed him.

"And you don't even know if she's yours," Derek pointed out.

"Even if she is, you didn't know," Derek added.

"I did know," Mark said quieter, leaning against the hallway wall.

"I knew when her mom got pregnant. She told me," Mark started. Derek looked back curiously. He found it strange that he had never told him.

"I gave her a couple of hundred bucks, and I left town, and I never saw her again. I figured she got an abortion. Hoped. But I did know," Mark added.

Neither knew what else to say. Derek just nodded in agreement, signaling that he empathized with him. But even without the paternity test results, it was clear. Mark was Sloan's father. There was no getting around it. But maybe this would be a good thing.

Mark had always been the brother he'd never had. Now Mark really was part of the family in a weird way. And this teenager could be exactly what Mark needed to finally grow up. It'd be an adjustment, but he knew he'd be okay eventually. Not long afterward, Addison, baby Nate stirring in his car seat, walked out of the room with Sloan following closely behind.

"So…now what?" Sloan asked.

"Well, now we wait," Addison said.

They all stood around awkwardly for another minute before Derek gestured for Addison to loop her arm around his. They gave both Mark and Sloan a nod before leaving to take their new baby home. Mark and Sloan stood around in the hallway awkwardly for a while longer. The only sounds between them were doctors shuffling around, working the night shift. They looked at each other curiously. Both knew internally that a paternity test wasn't necessary. Instinctively, they could feel it.

"So, you got somewhere to stay?" Mark finally asked.

"Uh…yeah," Sloan said. There was a shelter she could go to a few blocks from St. Ambrose, but she'd rather not. The one night she stayed at the hospital after the baby was born felt like paradise. And she severely missed having a clean bed to come home to.

"That doesn't sound very convincing," Mark couldn't help but comment.

"Well, I do have a place to stay. It's just…a shelter a few blocks from here," Sloan explained shyly. She couldn't help but think she was screwing up with her bio dad. They just met and she was already telling him she was homeless. And she'd already had a baby as a teenager, so she could only imagine what he thought of her.

"Why don't you stay with me?' Mark offered. Part of him didn't know why he offered. What did he know about taking care of a teenager? But it felt like the right thing to say.

"Really?" Sloan's eyes lit up. A clean and warm bed was all she could think about.

"Yeah," Mark said.

"But the results aren't even back yet," Sloan pointed out. Part of her wished she hadn't said that.

"I know," Mark said, debating if he should say what he wanted to say next.

"But I believe you," Mark said, deciding it was the right thing to say.

"You do?" Sloan asked.

"Yeah, I do," Mark said.

"And I don't like the idea of you sleeping at some homeless shelter," Mark couldn't help but add.

"Well, it's only until I get a record deal or something," Sloan said somewhat jokingly. She did have her guitar and used it to make a little extra money from time to time. And she did want to go into music someday. But it probably wasn't the best time to tell her new dad that.

"Then it's settled," Mark said, sounding more confident than he felt.

"So, what's your house like?" Sloan asked. Mark picked up one of the two garbage bags she left on the floor, leaving Sloan with one large garbage bag and a guitar case. Before answering her question, he couldn't help but chuckle.

Sloan continued asking multiple questions all the way home from St. Ambrose. And Mark had a million questions to ask her but refrained. He didn't know if he should ask about her living on the streets or what happened between her and her mom. Plus, Sloan didn't really give him much time to ask anything. It was overwhelming, but in a good way. It'd been a long time since he introduced himself like this. And he admired Sloan's constant curiosity.

When they got back to Mark's place, he showed her around to where everything was, from the fridge in the kitchen to the guest room. When he showed her the guest bedroom, Sloan couldn't help but let out a "wow". She looked back at him excitedly, which made him smile.

He couldn't help but realize this girl must've felt lost for a long time before getting here. She may have given birth to a new baby and lived on the streets for who knew how long, but she was still a 16-year-old girl. She couldn't help but drop her things near the door and flop onto the bed. Mark couldn't help but laugh.

"And there's a bathroom for you over here, with a shower and everything," Mark said after giving her a minute to digest. He opened the bathroom door and pointed inward.

"Oh my God, I haven't had a shower since forever," Sloan said, propping herself up by her elbows.

"Well, you're welcome to, if you want," Mark said, hoping his tone came off sincere and not awkward.

"Thanks," Sloan said. They stood around awkwardly for another minute before Mark said goodnight and went off to his own bedroom.

As for Derek and Addison, Addison carefully took the baby out of the car seat and into his new crib. Thankfully, Nate only stirred slightly when she did. Derek and Addison stared into the crib, astonished by their new addition. With one of Derek's arms slipped around Addison's waist, she leaned into him, resting her head against his chest.

"We have a baby in our crib," Derek whispered. Addison giggled at his excitement.

"We have a baby in our crib," Addison repeated, looking up just for Derek to lean in for a sweet kiss.

After watching Nate sleep for a few more minutes, they eventually made it back to their bedroom. However, it was only a couple of hours later when Nate woke them up from his cries. Addison offered to take her turn first, letting her husband get some much-needed sleep after weeks of working himself senseless. Plus, she could get maternity leave now but with everything going on at St. Ambrose, she doubted Derek would take time off.

"Hi there, baby," Addison said as she rocked Nate in her arms gently. After about 30 seconds, Nate's cries quieted, and he looked up to see his Addison smiling at him.

"Let's hope you're always this well-behaved," Addison whispered to the baby, who looked back at her, confused.

She giggled and watched him look around a little while longer before smelling him to see if he needed his diaper changed. Thankfully, the diapers were in the closet and not still packed in the garage somewhere. After that, Addison took him downstairs to heat a bottle.

Before they left last night, Addison grabbed some milk from the milk bank. After setting Nate into his car seat, she started warming up his milk. Addison made a mental note to open up the boxes of baby supplies and toys that she and Derek had lying around somewhere. Nate seemed perfectly content in his car seat, but she also knew he'd probably be more comfortable in a jumper.

Eventually, Addison picked him back up and fed him his bottle. As she did, one of his little fingers grabbed at hers. She couldn't help but smile and let out a quiet "aww" when he did. Actually, she couldn't stop giggling. Like it was some kind of "pinch me" mechanism. It was hard to believe that this was really her life now. If someone told her she'd be here five years ago, she wouldn't believe them.

As the milk got closer to emptying, Addison watched as Nate's eyes started closing sleepily. With it, his grip loosened. When Addison was sure he was almost asleep, she gently pulled the bottle out of his mouth and put it on the kitchen counter. As she brought him closer to her chest to rock him, she heard Derek upstairs.

"Hey," Derek said, sleepily leaning on the railing.

"Hey," Addison looked up for a quick smile before turning her attention back to the sleeping baby in her arms.

"What time is it?" Addison whispered after a minute passed.

"5:28," Derek glanced at the oven clock behind her.

"So, I guess he's not as good of a sleeper as we thought," Addison joked.

"It'll pass," Derek brushed off the lack of sleep they knew they were in for.

He walked closer to the pair, his eyes landing on the sleepy baby in her arms. They smiled at each other before Derek wrapped his arms around her waist from behind. It'd been almost two years, but they finally got their baby. They were prepared to bask in the moment as long as they could. And considering how peaceful Nate's sleep was right now, they definitely had the time to. But eventually, they both walked back to the nursery to lay him down in his crib before heading back to their own bed to get whatever sleep they could before he woke up again.

Back at Mark's place, Sloan woke up more relaxed than she'd felt in a long time. No uncomfortable pregnancy body, loud car horns, or crying baby to wake her. Just the sun peeking in through the curtain. The last time she felt this calm was when she lived with her mom. After getting kicked out, Sloan got used to sleeping on friends' couches and lumpy mattresses in homeless shelters.

"Morning," Mark greeted her as she laid out on the guest bed.

"Morning," Sloan said, cheerfully stretching out on the bed.

"Sleep well?" Mark chuckled.

"Yes," Sloan smiled. There was something about her smile that felt familiar. Actually, everything about Sloan felt familiar to Mark.

"So, I don't really have much food here," Mark said awkwardly, opening and closing the fridge door. Fathers were supposed to have breakfast ready for their kids.

"It's okay," Sloan thought nothing of it. It was hard to be picky when all she'd had over the past few months was whatever there was at the soup kitchens. Or getting McDonald's with whatever money she got from performing on the street.

"I do have a pretty killer espresso machine, though. If you're into that kind of thing," Mark added.

"Actually, do teenagers even drink coffee?" Mark thought aloud. Were teenagers allowed to drink coffee? It dawned on him how unprepared he was to take care of a child.

"All the time," Sloan laughed. It was nice to see him make an effort.

"Well, I guess I'll make us some coffee then," Mark smiled.

Mark left the room and Sloan took another shower, even though she had already took one less than 12 hours ago. She didn't know how long she'd be staying and she planned on taking every opportunity she could. After she got dressed, she could smell the coffee aroma coming from downstairs. God, she missed fresh coffee.

"I didn't know how you like it, so I have some cream and sugar if you're into that stuff," Mark pushed over the small carton of cream and sugar container. He liked his bone-dry cappuccinos, but he doubted a teenage girl would drink it that way, too.

"Thanks," Sloan grabbed the cream and opened the sugar container. She was a typical teenager who liked her coffee with plenty of cream and sugar. Mark winced at the thought, but reminded himself that her taste could change in the future.

"So…," Mark started, awkwardly.

"So…," Sloan repeated him in the same manner. Except she couldn't help but let out a small laugh after a bit.

"Your friends seemed nice," Sloan said, referring to Derek and Addison.

"Yeah, they're the best," Mark smiled. This felt like a lighter conversation starter than asking about her mom, which is what he really wanted to know.

"What are they like?" Sloan leaned against the kitchen counter, listening intently.

"Well, they're doctors. Like me," Mark gestured to himself.

"I've known Derek forever. And then we met Addie in med school at Columbia," Mark continued.

"Wow," Sloan commented.

"You think they'll make good parents?" Sloan couldn't help but ask.

"Absolutely," Mark said, without a doubt in his mind.

Sloan leaned closer, making it clear she wanted to know more.

"Derek has four sisters, and the Shepherds, they kinda became my family," Mark said.

"What about your parents?" Sloan asked.

"Everett and Madeline weren't really interested in being parents," Mark tried to explain as well as he could. But the truth was, they were distant. More than that, they were borderline neglectful. But as he got older, he realized his parents just weren't people who were ever interested in being parents.

"And you know, when we went to med school, we met Addie and then we became a threesome," Mark continued.

"Wait, you mean the three of you…?" Solan gestured her hands into a circle. She clearly thought the three of them were some kind of throuple.

"What? No!" Mark insisted. But he also couldn't help but laugh over Sloan's accusation.

"Addie and I, we kinda slept together," Mark admitted.

"Then why are they still together?" Sloan asked.

"Because they love each other," Mark said, simply.

"And what happened with me and Addie was a mistake. They were on the rocks for a while and it just sorta…happened," Mark admitted.

"Not that that's an excuse," Mark quickly added.

They both took a moment to laugh before Mark asked Sloan what he really wanted to know.

"What happened with your mom?" Mark asked nervously.

He remembered her mother. They weren't anything serious, but he still knew her as a generally kind person. He didn't know her well, but she didn't seem like the mean type. Though, even Mark knew that looks could be deceiving.

"She didn't exactly love the fact that I got pregnant," Sloan said, stirring her coffee and letting the spoon clink against the glass. Then Sloan told Mark everything.

When Sloan first suspected her pregnancy, she had her friend buy her a test. A friend with much more liberal parents. After peeing on the stick, she knew. She kept it from her mom until she knew she couldn't anymore. Her mother wanted her to get an abortion, and she refused. Sloan knew she wasn't ready to be a mother, but she also wasn't willing to get an abortion.

So, her mother dragged her to a clinic. When Sloan still wouldn't do it, she kicked her out. One day when she came home from school, she found two boxes of her clothes on the doorstep. And when she tried to go inside, the doors wouldn't open. Her mother changed the locks while she was gone.

With nowhere else to go, Sloan stayed with a friend for a while. Once her pregnancy hit six months, her belly bump became more prominent. By then, her friend couldn't hide it from her parents anymore. For a while, Sloan jumped around staying at friends' couches until she'd exhausted all her options.

She started staying at homeless shelters and busking on the street with an old guitar she brought along with her. With the little money she made from that, she bought food for herself and her growing fetus. And sometimes, there were some nice homeless people that gave her some food because they knew that as a pregnant teenager, she needed to be eating more to stay healthy.

Eventually, Sloan took the initiative to find her father. Years ago, her mother told her about Mark and how she got pregnant in college. She told her about how he was a womanizing med student who, after learning about her pregnancy, gave her money to have an abortion. If anything, she thought her mother would understand her current predicament. But no such luck. After researching online on a library computer, Sloan found Mark's name listed under St. Ambrose's list of doctors. Desperate to get off the streets, she saved enough money to bus her way to LA.

Living on the streets really made Sloan grow up. But even so, she was still a clueless homeless teenager that gave her baby away. One that was trying to be responsible but knew her limits. She needed more, someone to rely on, someone to take care of her. That person used to be her mother. And now that their relationship was ruined, all she had left was her father. Even if she'd never met him before.

"Wow," Mark commented.

"Yeah…so, here I am," Sloan added before taking another sip from her coffee.

"So, what about school?" Mark asked after pausing for a minute.

"What about it?" Sloan asked.

"Did you drop out? Or…?" Mark asked.

"I guess so," Sloan shrugged.

Mark thought to himself for a minute. Here was his 16-year-old daughter whom he never knew he had. She'd given birth to a baby, was homeless, and not in school. He didn't think he'd ever want to be a father, but now he was one. Whether he liked it or not. And despite Sloan's obvious ability to take care of herself, she deserved to have someone look out for her. Mark was terrified, but he knew he had to step up.

"What do you think about staying here?" Mark asked.

"Permanently," Mark added after Sloan stayed quiet.

"Really" Sloan's eyes lit up.

"Yeah," Mark said, feeling more on board with the idea after seeing Sloan's excitement.

"That'd be awesome!" Sloan exclaimed before hugging Mark tightly.

A/N: So, Sloan is definitely here to stay. And Derek and Addison are currently very happy with their new baby. I have some more ideas coming, so thanks for reading and catching up with this story. And trust me, that Addie line, "That is not how you bond with children!", is definitely coming at some point because I just love it. Hopefully a new update will be coming soon.

Update 8/6/22: I posted chapter 19 (i.e. the next chapter) but for some reason keeps uploading the wrong chapter (even though when I check, it's the correct chapter in the doc manager and everything) and it keeps doing it everytime I delete and reupload so if you want to read the next chapter, read it on ao3 ( /works/35431612/chapters/102302847) because it's not working here at the moment. I will hopefully remember to delete this bit when I get it to work again. Thanks again for reading, sorry for the inconvenience!