Consider: Problem child and Wei Wuxian look-alike Mo Xuanyu meets Sect Leader Jiang during his many visits to Jinlintai on Jin Ling's behalf. Sees how he regularly rescues Jin Ling from Jin Chan and the politely shitty people of the Jins and decides 'yeah I also want that please' so he sneaks into the Yunmeng retinue to go become a Jiang disciple.
Of course, everyone KNOWS where he went but JGS doesn't care and JGY thinks its an easy way to get rid of him as competition. But life in Yunmeng is significantly harder than Jinlintai because here he isn't a potential heir - he's just some random kid like everyone else and we all have to work the rice paddies and harvest during lotus season.
So it sucks, its tough, his ego and his body are bruised. But the people are... strangely nicer, despite being blunt? They don't mind his inclinations (the Jiang are an eclectic bunch and considering WWX's actions and all the rumours about the sect already they can't afford to be so picky nor do they care for reputation - people gossip anyway.)
Sect Leadee Jiang is, of course, a key part of Mo Xuanyu's psychosexual awakening (he maaaybe gets a little too interested in demonic cultivation when he attends a nighthunt with Zongzhu where someone is all tied up by Zidian...) and Jin Ling identifies him as yet Another Uncle at some point (cue JC freezing and being suspicious because of his looks only to realise he's actually just a paternal uncle, damn, WWX's return avoided.)
Somehow Mo Xuanyu gets: freedom from his shitty relatives (his shijie and shixiongs verbally berate anyone who tries to retrieve him), a chance at more normal family (Jin Ling thinks he's the fun uncle even if he's a bit shit with kids but he's TRYING and he trips Jin Chan on purpose) and??? Somehow???? Sect Leader Jiang tolerates him?
Cue failing seduction attempts (JC is too oblivious for) and tsundere reactions to more blunt appeals for affection, unfair comparisons to WWX and - eventually - a few ill-advised nights of debauchery and the two of them exploring things they thought they'd never have.
Then, well, canon has to happen doesn't it? Mo Xuanyu has no reason to practice demonic cultivation and doesn't live with the Mo family but he does still meet Huaisang at Jinlintai and does still find the manuals to bring the Yiling Laozu back. But he doesn't want to do it for himself - Jiang Cheng clearly mourns his brother and will never really move on with his life without some kind of conversation. He learns that the Lan's Inquiry doesn't work either but maybe he has a shot of contacting him.
Of course, Jiang Cheng vehemently refuses - how dare Xuanyu even suggest it?! How dare he try to practice demonic cultivation under his roof? Mo Xuanyu bristles, remembers the false accusations of Jinlintai, knows he's being unfairly compared, and storms off even more resolute to Do It. Maybe out of a sense of vindication (you always see him, maybe I should just be him!) Or else trying to prove his use to JC (I'll do this for you even if you think I shouldn't, it'll be worth it. I'll be worth it.)
Except it all goes 'wrong'. He didn't mean to bring WWX back in his own body. He didn't really understand the mechanics because of how well-obfuscated Huaisang's manuscript was. WWX comes back. Jiang Cheng comes looking for Mo Xuanyu. And now he's gone.
And with his words Jiang Cheng has lost yet another person he loved.
