I keep changing my mind about this. My mom has specifically asked me not to invite her and said she almost caused the breakup of my parents' marriage. I think my mom is being crazy. my brother and I didn't know about her til I was 12. Dad won't talk about it (she's his daughter), she's 12 years older. I talked to my grandmother and she thinks half-sister will understand if I don't invite her since things are weird between her and my mom. I would like her there but I'm not sure our relationship is strong enough to deal with any family drama that may come from it. She has an almost 2 yr old that no one else in my family has bothered to meet (I went to his birthday party and my brother sent a present). I've met her 4 times.. would like to be closer but super awkward and I'm afraid whatever I do will make it worse. My parents are paying for the wedding (and I will be staying with them that week). I want a way to resolve this without my mom or sister being hurt.