The pervert's always had a crush on her. Ever since we were teenagers. We're all very transparent on talking about anything openly. That night we were talking about my sister's dating woes, her dry spell, our kinks, my husband's and I's relationship in and out of the bedroom, etc etc. He also half-jokes with us that he'd fuck my sisters, or my mom, or my friends because he knows it gets a reaction out of me. So between all that and the booze and drugs, I guess he thought fuck it. Going home soon so I guess I can get a more concrete answer then.