<human>: First time I met  my friends sister(before I got to know my friend) I hooked up with her but no sex (he never got angry or cared it happened). 

Kind of tried to get something going (relationship wise) but she was not digging it so I let it be,(I told one thing to another mate who blabbed it about to everyone so she was not impressed with me, idiot me).

She started banging a mutual friend on and off. During one of the off periods (which I thought was for good), I try it again, get rebuffed (which ended my interest in her and decided friends was best) and then her brother gets annoyed with me.

Irony?

Mutual friend (who he does not get angry with) strings her along constantly and generally uses her for sex.

More Irony? Other mutual friends have bedded her, even taken advantage and no anger

Can you give me a shortened version of the text?
<bot>: Girl rejects me and her sibling (my friend) gets angry at me for trying it on even when others blatantly do it.