can I tell FH's brother he can't invite his girlfriend?

Oh dear I don't blame you. It's really her own fault if she's not invited...since they are so off-and-on I don't really think it's terrible not to include her...

Just reading the title I was thinking, of course you need to invite her. But now that I read the whole story, no way would I want her there. I think you have a legit reason to not invite her!

While there are always exceptions to the rule, it is considered very rude to not invite guests' significant others. If your future brother-in-law is still dating this person when your wedding rolls around ... you need to invite her.

One thing I recommend is having some sort of security, and warning them about her and her behavior. Enlist a couple of friends or family members to watch her behavior, and if they think that she's starting to ruin the wedding, call in security and boot her outta there.

Something I would keep in mind is that there is obviously a reason he keeps staying with her. Not inviting her would likely cause her to turn him against his family and isolate him.

I don't think you have to worry about this until very late March. Hopefully by then your FH's bro will have enough sense to break up with her for good!

Just address the invitation to the brother only. Also make it clear to him she is not invited. You can give him a line about not knowing their status. It's not unreasonable of you to not invite her given their vitriolic on and off again history. Why should you reserve a seat and pay for her to attend when she may not even be with him then? You could put that space towards someone you actually care about.

I wouldn't worry about it until closer to the wedding day...but I think it's perfectly acceptable. Then again...my FSIL's boyfriend isn't invited to the wedding. She was basically told that *her boyfriend/BD* isn't allowed in our house...nor is he allowed near our wedding. If she decides that she doesn't like that...then she can just not come. FH was firm with her. Make sure you and FH are on the same page with this though.

I am sorry to say this, but if you don't invite the GF then you can't invite the brother. Couples usually come to these events as a unit and rarely come alone. If this girl sounds as crazy as she really is then she will never let the brother come to your wedding alone. I am having the same issue with my fiancé's brother and his on/off fiancé. Neither of them is invited to our wedding because my fiancé and his family cannot stand her as a person. She is with him and so the least we can do is honor their relationship and just not invite them. Remember: if they are separated when the invites go out then it is safe to address it to him alone. You have some time before then, still. It's a hard choice to make and I wish you and your fiancé the best!

Since FBIL is in the wedding party, match him up with a single BM.

Hopefully, when you need to send out invitations, FBIL & on-again, off-again GF will not be together.

I would try not to worry about it until much closer to the wedding. Things could be so different by then (like he hadn't spoken to her in 6 months cause he realized she was out of her mind), and it could be a non issue. IF for some reason, he is with her close to the wedding date, I think you need to sit down with him and explain why you don't want her there, not just exclude her on the invite. You need to feel him out and listen to why he might want her there, and then try to come to a decision you both can live with. That is what I would do.

I would def wait it out til it got closer because, like you said, they will likely break up before then. Then when it comes time for the invites, make it clear

If your wedding is in May, you still have quite a while...hopefully they won't still be together by then!