Parent/child incest squick me. This is much more linked to the parent having raised the child than to any blood issue. Also, I am insanely squicked by Sirius/Harry. Even mentions of Sirius/Harry are enough to squick me. And I'd prefer not have to deal with Harry having an unrequited crush on Sirius. As for the opposite... I'm outta there, thanks. This may have something to do with my OTPs, though, which involve both Harry and Sirius in other pairings. (On the other hand, this kind of pairing doesn't squick me in original works; The Hunchback by Paul Féval, for instance, that's alright with me.)

Sibling incest don't squick me. I'm not all that much interested by Ron/ or Ginny/ -cest. Blame the OTPs.

I really like Blackcest, but I'm a Blackaholic, so there's the reason. And of those, Bellatrix/Narcissa is the one I like the least, because I'm an Andromeda-fan, and I always have the feeling the pairing seems to make a simple, stupid, bland goody-goody out of her. (And this is entirely due to my completely irrational mind, because I don't read Bellatrix/Narcissa and don't think I ever did. I only know how myu own mind works, and that's the feeling I get from the simple pairing. This has nothing to do with the fics or anything.)

Also, cousins isn't incest to me. It's legal where I live, so I never really looked at it as incest.