 If you liked
Kiss x Sis (TV)
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 ...then you might like
Isekai One Turn Kill Neesan: Ane Douhan no Isekai Seikatsu Hajimemashita
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These two animes are only related to one strong aspect that is onee-san loving their younger brother in a romantic way and wants to make their relationship more than just siblings.
Only the main theme of these animes are connected, other than that they are totally different. As "One-Hit Kill Neesan" is an isekai action anime (not much ecchi) and "Kiss x Sis" is a romance-drama (100% ecchi) anime . But there might be another thing similar, both of them can be described as Harem.