XOXO

It depends why you don't like him. Will he disrupt your day? Do you think you can enjoy your day with him being there? I would say that if it comes down to your sister being miserable because she is alone at the wedding, and you decide that you will tolerate and ignore this person, and you will NOT let anyone ruin your day, then invite him. I commend you for wanting to please others on your day. It shows you are the bigger person.

I would do what would make your sister happy- even if you hate him. YOU WILL NOT notice him that day- nothing will bother you, trust me.

I will say if he is abusive or has substance abuse problems and could cause an upset at your wedding then you have every right to say no.