Jay was out on an assignment with Adam Ruzek when he got the phone call he had been waiting for. It came from an unknown number, so he answered with no knowledge of who was calling.

"Jay Halstead."

"Good morning, Mr Halstead," said a female voice. "My name is Andrea Young, calling from SafeTest Clinic."

"Oh, morning," he said as a mixture of excitement and apprehension hit him. This was the call with the DNA test results. He was about to officially find out Jess was his sister. Or not. It struck him how badly he wanted the news to be good.

"Your DNA test results have come in, sir. The nature of your query was to find out if you are related to a Ms Jessica Sutton, correct?"

"That's right."

"The results confirm that you are related."

Just like that, he thought in delight. Jess really was his half sister. Her mom had told the truth.

"Oh, amazing! Thank you!" he said.

"You're welcome. Have a good day, sir. And thank you for your business."

"I will! I mean, you're welcome. Thanks again."

"Good news?" Adam asked from the driver's seat of his car as Jay ended the call. They were heading to track down a witness on their current case who was needed for a second interview.

Jay looked at his good friend and colleague, and he couldn't help grinning like a Cheshire cat. "That was the clinic where Jess and I got DNA tested the other day. They've just confirmed we are related. She really is my sister."

Adam smiled too and pulled the car over. Whether their journey took a couple of minutes longer was of no importance. "That's brilliant news," he said once the car was stopped. "Do you want to call her quickly before we get on with this?"

"Good idea," Jay said appreciatively as his brain started to catch up. As always, he was thankful for Adam having his back. "I should have thought to ask them if they've called Jess yet."

"If they hadn't before they called you, I assume they'll be doing it right now."

That was logical. Even so, Jay found Jess's number in his contacts list and tapped the icon to call it. His call went through and the ringing sound started. As he waited, he began to play out in his mind how he might break the news if she hadn't received it already. Disappointingly though, he didn't get an answer and voicemail picked up his call.

"This is Jess Sutton. Leave a message and I'll get back to you as soon as I can."

Jay ended the call before the beep. He wasn't going to leave their DNA test results in a voicemail. He imagined she was working on cleaning a crime scene somewhere, and would get back to him when she took a break.

"Do you mind if I call Erin real quick?"

"Have at it. We're stuck in traffic, right?" Adam said, looking studiously out of the windshield at the almost empty road.

Jay chuckled and called Erin's number. She was probably in the bullpen. That was where she had been when he and Adam had left less than ten minutes earlier.

"Hey," Erin said. He could tell just by her tone that she was indeed still in the bullpen.

"Go in the locker room for a minute," Jay requested. He didn't think Voight would go ballistic about the personal call if he found out about it, but he figured there was no point taking the chance.

"Alright," Erin said. Then a few moments later, "Okay, what's up?"

"Just got a call from the DNA clinic. They confirmed Jess is related to me. She really is my sister, Erin. Her mom's story was true."

"Well that's great news. I'm really happy for you both," she said brightly. "Have you call her yet?"

"Just tried, but no answer. She's probably working."

"Makes sense. When you do get her, invite her to dinner at my place and find out what night works for her. I'll cook something."

"Thank you. That'll be a nice time."

"I'm looking forward to getting to know her more. Someone so switched on, with their life perfectly in order. I can't relate."

Jay laughed. "Right? Maybe we can find out what the secret is?"

"Better get back to it, Jay. Congrats again, big brother."

Erin ended the call, leaving Jay thinking about being a big brother. What did that involve? What new responsibilities did he have now that he had a little sister? Or was that overthinking it?

With the call finished, Adam got the car moving again. For some reason, maybe the emotions of the moment, Jay felt a desire to confide in his friend.

"A new sister isn't the only thing I've got going on," he said.

Adam glanced at him. "Oh?"

"This is very strictly between the two of us. Don't even say anything to Kim. Erin and I are trying for a baby."

Jay saw Adam's eyebrows raise for a second, probably thinking about how soon that decision had been made after Erin's return. It would be hard for other people to understand the depth of feeling and commitment that already existed between them.

"That's amazing news," Adam said. "You guys will make outstanding parents. As for not telling Kim, are you for real? Erin will have told her already."

That was a good point, Jay had to admit. But still, he didn't want the news on the rumour mill at the 21st. "Maybe. Just keep it under your hat for now, please. What's fatherhood like? As awesome as I imagine it?"

"Better, in the good times. It's a lot of hard work too, especially when you're both cops. Get ready to forget what sleep is."

"Trying to talk me out of it?" Jay asked with only a hint of humour.

"Not at all. Being a dad to Mak is the best thing I've ever done in my life. The only thing I've never fucked up, and I'm so proud of that."

"She's lucky to you and Kim as her parents. Very lucky."

"Your kid will be as lucky, and Jess is lucky to have you as a brother too."

"Now I've just got to live up to it," he said, as much to himself as to Adam.

"Bro, seriously? Jess is only starting to get to know you and she already thinks the world of you. Kim and I were talking to her at Hunter's and I was putting you over a bit. I'm not going to get into repeating what she said because I don't roll like that, but yeah, safe to say she's really happy with how it's going with you. Honestly? I think she's a workaholic and therefore doesn't have much of a social life, and I think she might be quite lonely. Meeting you has changed that for her."

"Especially because she just lost her mom," Jay said thoughtfully. Until now, he hadn't put much thought into the fact that although they had only recently met, he might be all Jess had in the world. No doubt she had friends of course, but maybe not close ones. First job as a big brother, he decided, was to make sure she wasn't too lonely during the grieving process.

It was that evening when Jay finally got a call back from Jess. He had tried to contact her a second time in the afternoon before resolving himself to wait until she called back. Now he was at home, about to get ready to head over to Erin's place for the night. Seeing Jess's name on his phone's screen made him smile.

"Hey, Jess," he said after answering.

"Jay, hi," she said, sounding somewhat tired. "Sorry, I missed two calls from you? Been working on a fentanyl lab today, left my phone in the van and forgot about it all day. I just got home."

"You sound tired," he said with concern, not wanting to immediately drop the news on her. He figured she hadn't gotten it herself yet or she would have opened with it.

"It's a long day in this hot weather, working hard with all the PPE on. Not sure it's meant to be humanly possible to sweat so much. Too much info?" she added with a giggle that Jay found endearing.

"Maybe a bit,' he said, sharing in the humour. "So, did you get any other missed calls today?"

"A couple. You're the first one I called back because... Wait, did the clinic call you with the results?"

"They did, and it was great news. They said the tests proved we are related." As he told her the news, Jay had felt the delight build up in him again.

Jess made an excited noise on the other end of the call. "Yes! I never doubted my mom, but it's so good to get confirmation. Now it's official we should do something to celebrate. I've been thinking I wanted to get together with you again. I enjoy your company."

Enjoy it and need it, he wondered. Even if that was the case, he didn't expect her to say that. "I enjoy your company too, Jess. So does Erin, and she's really happy for us both about the results. She's offered to host us both for dinner to celebrate. Wanted me to ask when would be a good night for you?"

There was a moment of silence. Jay imagined Jess checking her mental calendar or diary. "That's such a nice offer. So kind of Erin. How about Saturday night?"

"I'm sure that will work. If not, I'll call you to re-arrange."

"Sounds like a plan. Hey, Will called me yesterday."

"He did? How did that go?"

"Kind of awkward. I mean, talking to a new relative you've never met in person is an awkward thing to. There was a bit of a feeling I got, like he had called me because he felt it was expected of him more than because he wanted to talk to me. We were only on for about ten minutes. I came out of it feeling a bit low."

"Sorry," Jay said, hardly surprised. What else was there to say? Will was Will.

"There's nothing for you to apologise for. I felt you should know he called is all. Are you doing much this evening?"

"Getting ready to head over to Erin's. Quiet night in with a movie." And more sex, he obviously didn't add, but he was looking forward to it. "How about you?"

"I've not long got home. Going to take a shower, have dinner, then get to work on some editing for the next video for my cleaning channel. If you've ever wanted to know how to properly clean a glass shower screen..."

"Can't say I have," he replied, reciprocating her humour rather than mocking her work. In all honesty he still couldn't get his head around how Jess had managed to get a YouTube channel past two million subscribers by offering cleaning advice. He made a mental note to check it out sometime. But not now. Now he had to get over to Erin's. "I should finish getting ready, Jess. Glad I got to be the one to break the awesome news to you. I'll look forward to seeing you Saturday."

"Me too. See you then, Jay. Goodnight."

"Night," Jay said, and hung up.

A/N: It's official – Jay and Jess are related.

Jay is starting to look ahead to fatherhood, but how long will they have to try before Erin becomes pregnant?