Modern AU where for X reasons (that don't involve any death because I'm soft tonight) Wei Wuxian loses contact with the Jiangs for over a decade. In that time he meets & marries Lan Wangji and they adopt a kid.

Throughout that time they move a lot because of work, so A-Yuan can't make many friends until they eventually settle down. One day A-Yuan brings a schoolmate home, which makes his dads just as excited as he is.

The kid looks really familiar, for some reason. Wei Wuxian spends the afternoon staring at him, so intently that Lan Wangji has to politely tell him that he's being creepy.

It doesn't click until Jiang Cheng comes to pick Jin Ling up.

Afterwards it's all very awkward because there are many things both Wei Wuxian and the Jiangs need to talk about, and their relationship is Tense; but they can't just tell A-Yuan and Jin Ling to stop being friends.

They tried, at first, to pit the children against each other, Jiang Cheng behind Jiang Yanli's back and Wei Wuxian behind Lan Wangji's. It didn't work and it got both of them scolded.

So they resign themselves to meet up for school events often and try their best to be civil. Because they are mature adults who can put their differences aside to Think Of The Children, even if they snap at each other when nobody's watching every now and then.

Ironically, it's Lan Wangji, known Jiang Cheng hater, who ends up helping the most. Everytime Wei Wuxian complains, he agrees so vehemently that after a while Wei Wuxian gets protective over Jiang Cheng instead.