I'm gay because of my gross whore sisters, why won't they accept that?

I had four sisters growing up and no brothers or a Dad. I am openly gay something that my sisters love to talk about and quite a few times we have gotten into arguments as to why I am gay. I KNOW it's because of them because whenever I even think about being with a woman my sister's faces pop into my mind and turns me right off. (I saw my sisters naked WAY to many times this also does not help) but they think I'm gay because I never had a Dad and grew up around girls but I am not effeminate at all so I don't think that's true. Do you think my reasoning makes more sense?