Hey I've been going through your NFHCC AU tag and I absolutely need to know when Eliot decided to tell Nate and Sophie hes a triplet. Like, did they run into them on a job and are they confused? Or did it just randomly come out one day?

Oh man, I can't believe I have an actual answer for this rather than just speculation. Thank you for asking ^u^

This is a bit of a spoiler for The Hitter Job, Extended Edition, but Nate and Sophie aren't actually the first ones to discover Eliot's blood relations. It's Hardison!

After discovering that Eliot Spencer has only existed for just under 2 years, Hardison, in innocent curiosity, digs in and discovers Eliot's real last name is Stone, and he has two brothers. He doesn't immediately go to Nate with the information, because the deeper Hardison goes the more information he gets and the picture this new information keeps getting worse. Only when Hardison feels comfortable and able to tell Nate about Eliot and his secret brothers and last name (amoung other more upsetting info) does he actually do so.

So for a while only Hardison and Nate are aware of Eliot's brothers and father, and they keep it that way. Nate is, of course, hurt that he didn't know this about one of his kids (it's a similar emotion to when he met Archie) but Eliot is almost 18 and Nate knows how easy it would be to loose the trust Eliot has in him, so he says nothing about it. I don't think it's until a job almost a year later, when the Stone triplets are all 18, does the Leverage team accidentally cross paths with both the Librarians and the Cebu trio.

It's a mess lol, but the mess ends with Eliot, Alex, and Jake all reuniting after 3 years of being apart, and the Leverage team and Librarians (as well as Kai and Ernesto) finally meeting their respective triplet's brothers and friends and guardians.

So while Nate finds out about Eliot's brothers before Sophie, and while Sophie isn't exactly happy Nate kept it from her, Sophie Devereaux (and Parker as well) is absolutely the one who understands why Eliot changed his name and never told her or Nate about his brothers. And while both Nate and Sophie aren't glad they find out by accident and not because Eliot chose to tell them, they understand why he didn't, and most likely never would have had the crossover not happened.