1. You must either live in the US or have concrete plans to relocate to the US. You also must have filed taxes for the 3 most recent tax years (assuming income is above the filing threshold). Your Aunt can serve as a Joint Sponsor, but that does not negate the need for your domicile or tax situation.
2. You fill out an I-130 for each person (3). Your sister will NOT be able to immigrate with your parents. They are different visa categories. Through you, it will take 20+ years for sister to immigrate to the US.
3. See #2 above.