sis best friend and bf

I've been having sex with my older sister's best friend and her boyfriend now for three years since I was 16. My sister has no idea and we don't want her to know because she'd go crazy on us. I think of them as my boyfriend and girlfriend. I know its mostly about sex for them but it means more to me. He is 25 and she is 22 which is my sister's age.

The first time was on a night when she invited me out and my sister was at college. We went to her boyfriends apartment and drank and smoked in his room. Then me and her made out and had oral. Then she talked me into letting her boyfriend fuck me. He was my first and so far only guy. I've had sex with her a lot too.

Every time I've had sex in my life its been with the two of them at the same time. I feel like I love both of them. I love making out with them and giving them oral and I always do whatever he asks because it turns him on so much. He likes to have me and her lie next to each other while we masturbate because he like to see us cum. I always feel self conscious at first but I always cum so hard hard. Someday I will want a real boyfriend but for now this is nice. I just wish I could be with them all the time.