Ms. Manicure:
Generally, you can only apply for membership through the chapter at the school you currently attend, unless there is no chapter there. So no, you can't attend rush at two schools, unless you have transferred to the second school and meet all of the requirements for membership there.
Your best bet is to seek out the women of the chapter at your school and inquire about requirements for applying for membership into their chapter. Also, our national web site,
www.aka1908.com, can give you some insight into membership prerequisites, including grades, credit hours, public service and character requirements.
If your family members belong greek organizations other than the one you're interested in, I don't see how that would be an issue. I think I can speak for my sorors when I state that none of us care whether your relatives are/were members of the other fine NPHC sororities. We only care about you and what you bring to the table.