Within incest fic what are some of your favourite tropes and themes?
I have a huge soft spot for moms being obsessed with how hung their son is and not being able to help themselves
For parent/child I love the college glow up. Kid leaves for college awkward and shy, comes back filled out, confident, and smokin' hot, and the parent has that oh moment. I also like white knight tropes, like parent being abused/mistreated by their spouse, spouse either finally leaves or child chases them off, then shows the parent what love is supposed to be like.
I also reeeeaaaally like mom/son cucking dad. Like the dad's totally into it, getting off on it, and the son basically takes over as man of the house. I also like where the son is bi and uses dad's cuck kink to evolve into fucking both mom and dad, even tho dad is straight.
I don't usually like stepcest, but I have a thing lately about, like, son's into mom's new husband, thinks he's seducing step-dad, only to find out later that step-dad had a whooole plan and son finds himself in the middle of mom and step-dad and loving it.
With siblings I really like stories where they leave and go somewhere nobody knows them and live publicly as a couple. Or with same-sex siblings in particular, where they live together their whole lives, never have relationships, and are seen as either "those weird but harmless hermits" or "those sweet siblings, aren't they precious."
For incest of any configuration, I like comfort after a breakup. I really like stuck fic, too, but I haven't found much of it. Y'know, mom's stuck in the washing machine, sister's stuck sneaking out the window, brother's stuck half under the bed, nearby family member takes advantage... Also! Stories where an outside party breaks in and forces the family to have sex. Oh, and pregnancy. I love a good breeding fic.
A couple things I don't like tho, that I see a lot of in breeding fic, is multi-generational incest (son knocks up mom, that kid also has sex with one of the parents, etc) and way too many kids. Like wayyyyyy too many. Why do so many incest fics have more than 5 kids?! Three is more than enough.