Scum Villain AU where Yue Qingyuan is also Tianlang Jun's nephew.
TLJ's sister liked to get around, okay? She was a free spirit! Experimental! She didn't just go right to fucking a snake, a couple of years prior to that she was carousing her way through the human realms, bringing back the sorts of thing that sparked her younger brother's interest and hooking up with whatever humans took her fancy. Which wasn't very many (boring) but there was this one brothel madam who caught her eye, extremely creative woman, would have been all over figuring out the logistics of snake-fucking if TLJ's sister ever needed the help. They had quite a few good times together, some of which involved third or fourth or even whole crows of others.
So after a few such revelries, TLJ's sister falls pregnant. She could abort it herself with just a nudge of her blood parasites, but the brothel madam is like no way any child of yours would be amazing, if you don't want it then give it to me instead! And TLJ's sister is like, sure that seems like an appropriate "thanks for the memories" type parting gift before I have to head back to the demon realms, and sticks around long enough to bequeath the newborn to her.
Unlike Zhuzhi Lang, she doesn't mention this part to her younger brother. Mostly because she doesn't have any reason to think that Half Human Jr will have any problems in his life. He came out looking normal, he's in the human realms being raised by the best human she knows, he's probably gonna have a great life. Way better than the boring crap purebred Heavenly Demons have to put up with!
Well, the brothel madam actually does adore the little guy, but while Yue Qi is still a baby her fortunes change. Her establishment runs afoul of a powerful public official, some of their competitors get nasty, and within a few years she's been poisoned and Yue Qi has been sold into bondage along with all her other assets to pay off her debts.
Things progress more or less like usual until the sects are setting up their ambush against Tianlang Jun, and Yue Qingyuan goes to fight him and TLJ is just like "wait a minute" and calls a time-out to ask him some pressing questions about his parentage. Which catches Yue Qingyuan just off his guard enough for him to notice that TLJ doesn't actually seem to be a bloodthirsty monster hellbent on destroying humanity, which in turn calls into question some of the Huan Hua Palace Master's claims...















