Boku wa Imouto ni Koi wo Suru, Yosuga no Sora: In Solitude, Where We Are Least Alone. Recommendations
Both involve love between a twin brother and sister.
It's similar to the last part of Yosuga no Sora, It has no erotic scenes, but still it's a catching love story.
both involve incest but BokuImo is a shoujo manga adaptation(in later chapters of the manga-not in the OVA-it is revealed they are not actually siblings) and Yosuga no Sora is a bishoujo eroge adaptations(they are actual brother and sister)...also Yosuga no Sora has fanservice while BokuImo,being a shoujo,has almost none
Because there is a "forbidden" relationship - sister x brother.
Both story is about incest.
-Dramatic love "twincest"
Both have incestuous relationship , with Sora one being more lustful. Boku wa Imouto is more oriented toward Love/romance.