 If you liked
Saikin, Imouto no Yousu ga Chotto Okashiinda ga.
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 ...then you might like
Eromanga-sensei
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Not-blood-related incest series in which the step-siblings' recently married parents aren't around to get in the way. The sister is initially apathetic towards her brother, but events take them from "strangers who happen to live together" to an actual family and potentially lovers... assuming one of the other haremettes doesn't steal him away. Of course, these events tend to be shamelessly lewd: Eromanga pushing the boundaries of what vanilla fanservice means, and ImoCho basically putting the hapless sister through a new fetish every episode.