Derek tried his best not to sigh. But he did.

His son was sat at the top of the slide, dripping wet. Like literally, physically, pouring with water from his clothes. His regular smooth blonde locks were glued to his face, water running down the sad crease lines of his face. Derek didn't think he was crying but he supposed he could have been.

He was promised ice cream. Then he got three water balloons, a water-pistol and two laughing sisters instead. It was a good couple of liters he got to the face. Or at least, it felt like a good couple liters.

He didn't hate them. But he did. He didn't love them either. But he did.

"You know how horrible it is growing up with two sisters-" Derek started as he paused by the bottom of the slide.

"Don't remind me." He murmured, not bothering to look up. He knew who it was. Of course he did.

"Well, times that by two."

His head shot up at that, the back of his cranium almost hitting straight into the bar above the slide. He was much too big for it now but he ignored that. He just needed somewhere quiet. Somewhere with fresh air. Somewhere, while not necessarily in the sun, that had an open sky. In fact, he sounded an awful lot like his nature-obsessed dad. "Mom is pregnant? With twins?"

"No, no, no, no. Don't worry. Mom is most definitely not pregnant." He corrected quickly, not wanting him to stay that freaked out for any longer than he had to be. They had Acetylcholine and Blue, which Zola and Bailey had dubbed their 'fluffy brother' and 'fluffy sister' but unless there were any unexpected surprises, they had settled on three. "I mean me. I have four sisters."

His chest depressed at that. Panic over. "And they have a thousand kids each. Well, except Amelia- she's slightly more sane."

"Mmm." Derek agreed with a murmured. While she may have been insane with other aspects of her life, Chaotic Amelia being Chaotic Amelia, at least she didn't have six kids like Kathleen.

His son shuffled forward a little on the slide and Derek took that as a cue to pull himself back a little from the slide. Despite the fact he was too old for the playground equipment, he still just about managed to get down the slide. He stood up from the edge of the slide, only just realizing his dad had a blue towel on his lap.

He smirked as he chucked the towel at the boy and it landed splayed out on his head. He pulled it off to expose a smirk before settling on a swing, patting his bare arms dry. There was no saving his t-shirt or jeans with a towel; he'd have to go and get changed.

"You know…I also kinda had a brother." Derek confessed, oddly quietly as he watched the boy scrub his hair with the towel.

He paused his drying, head tiling a little. "A brother? I thought you just had sisters."

"Not a genetic brother." He explained. "He was a friend from school. His parents weren't that great so he spent a lot of time at my house. Like- a lot of time."

"Was he a good brother?"

"Kiss, marry, kill. Mary. Judy. Olivia."

"Kiss and marry Olivia because she's hot, and kill you because I'm trying to focus and you won't shut up." He joked as he looked up from his textbook for just one second.

"Fine. Kiss, marry, kill. Covalent bonding, metallic bonding and iconic bonding.

He smirked, and rolled his eyes.

Was he a good brother?

"Thank you. Thank you, thank you, thank you." Derek said as he slipped into Mark's passenger seat.

"Okay- I have to know...what was so bad about her that I had to come and pick you up twenty miles away?"

"She said that she went on holiday to France."

"Right." He agreed, wanting to hear more. Flying to France didn't sound like a bad thing.

"She flew across the earth, not round it."

He snorted. "Oh, dear lord. I'm no longer mad about having to pick you up."

That was an excellent question.

"Do you want me to come with?" He asked, unsure.

"Um-" Derek hesitated. "I don't know. Do you want to?"

"You're doing that thing where you ask me what I want to do because you don't want to force me to do something."

He smirked sheepishly. "Maybe."

Mark sighed. "Well, off we go then."

"Yeah, he was a good brother." Derek agreed as he smiled a little. Really, he should have added a 'but' to that. He was always a good brother, but that didn't mean he was always a good person. "We played at the park and- oh, one time, he was teaching me like baseball and I wacked him right in the face and gave him a black eye. That wasn't so great."

Bailey smirked.

"He would come round for dinner most days. I even got him to come to like two of my school concerts - he wasn't a big fan of concert bands nor jazz." He continued. "He was my brother, even if he wasn't my brother-brother."

"Does he live in the other states like Liz and Kathleen and Nancy?"

He swallowed. "Mark was Sofia's dad."

"Oh. He died." Bailey said after a long moment.

"Yeah. He did." He confirmed in an unusually quiet voice. Mark's death still hurt, an awful lot.

It wasn't often that Derek Shepherd had an emotionally-driven conversation with his son. He supposed one day, when he was older and a little more mature, they would talk about more serious things like crushes and bullies and the stress of exams and whatever else his son would find hard in life, but he hadn't had many difficult conversations so far.

His eyebrows creased with concern. His dad had a brother…his dad used to have a brother. As much as he despised the wide selection of torture techniques they had invented to abuse him with, he did still love them.

He loved his sisters. He most definitely did.

"Must have been sad. Sounds sad."

"It was a long while ago." He shrugged, as if it didn't still hurt.

He slipped off the swing seat, pausing in front of his father. "But it's still sad?"

He paused for a second, pondering that question. "A lot sadder than I let other people believe."

"What does that mean?" Bailey asked, head tilting a little.

"I didn't like to cry in front of other people or anything like that." He explained. "Which is a really bad thing to do, emotion-wise. Talking about your feelings is always better than bottling them up inside."

"Why?"

"Because it helps to talk to people." He explained.

He nodded, but didn't reply for a good few seconds before inquiring, "I was like- a baby when you were in that accident, right?"

"Mmm." He agreed. It didn't sting like it used to, but his son talking about it hurt an awful lot more than anyone else.

"I don't remember much but if that happened now, I think that's what I'd do too. I wouldn't want to be sad...it makes Mom upset when I'm sad."

"I make Mom upset when I'm sad too. But I also make Mom upset when I say I'm fine and I'm not which is why talking to people about how you feel is so important." He explained. Bailey needed healthy emotional-processing techniques, unlike, earnestly, both of his parents.

"But you pretended not to be so sad about your not-brother?"

He swallowed. "Your mom is very strong when it comes to her own life. Bad things can happen to her and most of the time, she can handle it quite well. But she can't handle bad things happening to the people that she loves quite so well. Especially you kids."

"Contagious sadness."

Derek smirked. "Mmm mmm. It's a Mom thing. A parent thing."

"Do you get sad when I'm sad?"

"I remember after I was discharged from hospital, you were so young that you didn't really understand what was going on. And I explained it to you. And you cried. And I cried too."

"The contagious sadness made you sad, because I'm your son?" He suggested.

"My baby boy."

"Ew. No, Dad, no. Babies are like one to three or something. Like Elle or something. I'm not a baby."

"You'll always be my baby. My adorable, beautiful baby boy." He teased.

He rolled his eyes. "You know when you say you worry about what I'll be like as a teenager. You say you don't want me to become distant or whatever. Well, when you say things like that, it really makes me want to just run away from home, never mind stay out all night with my mates."

He smirked. "You know that's why dads exist, right?"

"Dad."

"Yeah?" He replied.

"I think I'm going to go and see Zo and Ellis. I was mad, I shouted a little and-"

"Yeah. I get it, it's okay."

"Hey- Mom said you wanted me to come outsi-" He paused as he was bombarded with an assult of water balloons. "Oh! God!"

He heard the sound of children giggling and turned around, only to see Zola, Ellis...and Bailey.

He smirked at the pair. He wasn't mad; he was overjoyed that they were bonding and spending time together, but joked anyway, "Bailey, that was not the moral of my story!"