I'm having a major dilemma. As you all know, I was a single mom for 4 years and Matt has never met my ex, and CS is sketchy at best. Sister A just had her baby in July last year and the dad ran off to California so no one could find him, so far, it's worked. Sister B was raised by my parents (our dad, my mom) because her mom ran off and never had anything to do with her and never paid for anything to help her out.

Sister B just recently got divorced and has had a few boyfriends, which I encourage as she needs to get her feet wet again. However, now she's settled with one. She moved him in after a week, he takes advantage of her, barely works, hasn't seen his kids or paid child support for the two of them in over four years. She's seen the bill, and he's in the hole 20k and about to get drug into court.
I do know, for reasons I won't go into here, as I think I've aired enough business, that this is the case. He doesn't see or care for his children. How she can even stand to look at this lump is beyond me, much less entertain thoughts of a future and family like she's doing.

Getting into my personal dilemma here, I can't stand how she parades this asshole around my family and Sister A like it's no big deal and he should be treated like family because he's living with her. Thankfully, I live a state away so I don't have to deal with it on a regular basis, but of course, my wedding is coming up. I'm getting married in the state they're in, so she'll be coming and thinking she'll bring him. (if they last that long, which they probably will if for no other reason than to irk the hell out of me. I know, I'm exaggerating, but there's a good chance they'll make it the next 9 months)

I do not want this deadbeat at my wedding. I feel it's disrespectful to me, Sister A, and to my SO who's raising a paternally forgotten child, to have this person brought in to celebrate my relationship, eat my food, drink my wine, and dance to my music.

How do I address this with my sister? I know there's probably no way to do it without a fight. Our relationship has always been strained at best., I don't see this as particularly improving anything. My mom suggested sending an invite without the "and guest" on it, but I want to make it explicit. We all know that sometimes people don't take the address into consideration and assume that partners/kids/kid's partners are included so they just show up. I want it to be absolutely crystal that under no uncertain terms is this person welcome at my wedding.

*also, I just got out of the hospital not too long ago, and plan to be around a lot more!