I have the privilege
of having two sisters too, both younger, and all this incest in anime never creeped me out either. Being the brother of a sister doesn't mean living together with a cute female that just waits for you to sex her when she's finally old enough for it, it's about living with this annoyance from day one until the day either of you moves out.. The feelings that develop over time there are very far from romantic. Let me link you to the
Westermarck effect for a more scientific view on that.