I generally feel that way about every game I play that feels a need to include the incest plot lines period. Since whether the text says "sister", "cousin", "landperson","friend", ect ect ect....the end result typical just always guarantees one of the exact same sexual encounter progression path setups with a character I've already played through 1000x before.
But I've also found not sweating and looking beyond the small stuff goes a long in finding your own enjoyment in these games a lot of the time. It's the characters themselves that make or break a game or it's attraction value to me...not the text relationship label assigned to them.