What to do with my biological father?

I'm sixteen and live with my step-dad, my real mom and four half-siblings. Technically five since my mom's pregnant. I've never met my biological father and he has recently tried to reach out to me after sixteen years of no contact. He wants me to move in with him and wants me to call him dad which is just TOO MUCH. Anyways, he invited me over to his apartment to get to know him and his girlfriend and son. (technically my half brother from another mother,I know it's really messed up) As I walked into the trash that was his apartment, I met his girlfriend and my half brother Gabriel. I was expecting a young kid like between8-12. he is sixteen and a half! Never have I felt so sick. My dad got this tramp pregnant when he was married to my mom! he cheated on her and then had me and wanted nothing to do with me for 16 years but he was still raising his son. I don't know what to do. I hate his girlfriend and at the moment I hate my life. I want nothing to do with Gabriel either. What do I do? My dad is practically harring me to be happy with him and wants me to move in and get to know Gabriel and his skank mom. I feel sick. Gonna go get an aspirin.