Thinking about Tianlang Jun x Su Xiyan x Mu Qingfang
All set during pre-canon where MQF finds snaby ZZL and takes him to the sect because he's a weird looking baby and that's cool.
TLJ and SXY find out and decided that SXY has to go rescue their snaby because it won't do any good that a heavenly demon goes to a righteous cultivation sect like Cang Qiong Mountain. So it's all up to SXY.
With some excuse SXY starts to spend a lot of time with MQF to figure out where ZZL is but finds out that he's just hanging around on MQF cottage and he's actually being taken care of (MQF is hiding ZZL from his shizun so she doesn't try to disect him yet+ he's also attached)
SXY and MQF actually get along quite well, specially after she found out that he was working on a posion that insta kills anything (she suggest testing it on her old hall sack teacher)
TLJ is hearing all the fun things they are doing and wants to join too so SXY organizes a date (she knows that MQF is chill, like, he's taking care of their snaby with love and care)
And they go on more dates and they all have fun and live happily ever after