Why do I do this to myself?

So you all know that I like that one guy, but there is this other guy that liked me…he found out who I liked too…Then today the guy who knows who I really like asked me out…and because early this weak the guy who I do like had told the guy who likes me that he doesn’t like me…I told the guy that asked me out I would go out with him…but then I had this talk with someone and I realized I can’t go out with this guy. See my mom married my dad without really loving him and now my sister is dating a guy that she doesn’t really love but moight marry someday and I don’t want to be like them…so how do I break up with this guy…I want to do it in person because that way at least im not mean by doing it in an email but then again im not sure…help again!!