 If you liked
Kiss x Sis
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 ...then you might like
Aki-Sora: Yume no Naka
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Same premise, boy with a sister complex although there are two sisters who both share an interest in their younger brother; they are unrelated by blood so they don't try and hide their affections. It's more of an ecchi comedy with tons of fan service and the sisters have the Loli effect going for them. Animation is good too ;)