Tropes that just won't die, eh? Tropes that need to be shoved through the airlock during an interstellar mission? Tropes that ought to be dunked in lighter fluid then fed to a dragon?
The whole Incest is Best thing. Like, really? REALLY? Even the allusion to it needs to be dropped into an active volcano. Sexual abuse is horrible on any scale, regardless of gender. Rape as character motivation or punishment is so ingrained in spec-fic that it's more shocking to not encounter it. Stories that add Keeping It In The Family as an extra layer of brokenness? Ugh. DNF. Instant wall-banger.
Yeah, yeah, "but it happens" and "history is full of examples." So? Fantasy in the 80s was rife with sibling sex. Hell, there was required reading in school involving that shit. Fast-forward 40 years and low and behold, that damn trope is back. Worming its way into popular SFF, again. More than just that one super famous series that made it to TV or even that other semi-popular book-to-show series. More than that next one you're thinking of too.
If you want your character(s) to be really fucked up, you don't have to have them fuck their family. FFS.
~wanders off to find brain bleach~