Quote from Rachel in The One with Rachel's Sister
Rachel: I cannot believe that. I mean, I don't really like it when Ross goes out with anyone, but my sister? Isn't that like incest or something? Oh, my God, and they're gonna have sex. Oh, no. And what if he marries her too? This is just terrible. This is just terrible. And I can't stop it. I don't own Ross, you know. And Jill should be able to do whatever it is that she wants to do. Oh, my God, I can't believe Ross is marrying my little sister.