Everyone needs to think about why this discussion was started. First off, I am not in a sorority and I do not have first hand experience on this subject. But as I was reading all the replies, something caught my eye and prompted this response.
USUAL SUSPECT says: Remember the true meaning of brotherhood and sisterhood.
I have 3 sisters of which I am the youngest. All of them are blood sisters, but my oldest is not my mother's child. There will never be a day that I would disregard her because she CAME INTO my family by way of my father and not my mother. All I am saying is that think of it as your blood. Your sister is your sister, and a brother is a brother, LOVE them like any other.
Peace be with