same, but they look too much alike so I think they're related :/ (unless they do the same they did to OniAi)
Oniichan dakedo Ai sae Areba Kankeinai yo ne. I don't want to spoil you since you maybe check it out, but it also has a brother-sister relationship (actually, the sister really loves her brother) but with a small surprise at the end.

I ship them... So, I really want them to not b blood related... I don't want incest