Does my Fiancé's Brother's Girlfriend have to come to my wedding?

She needs to be invited... How would you feel if you weren't invited to your future brother-in-law's wedding, knowing you are engaged to him? Yes, invite her, no matter how badly you don't like her.

Yes you should invite her. You will be so busy you will barely have time to even see her. She won't be there all day until ceremony/reception anyways.

Yes

you won't be getting to know your FBIL at the wedding anyway... don't worry about it, you'll likely not even notice she's there... unless she's a real nightmare or something! LOL

What @MNBride said! And the basic rule of being in an adult committed relationship is making the effort to get along and include their family even personalities may not mesh.

Yes, his girlfriend needs to be invited. Plus ones are only for truly single guests. Guests with SOs (married, engaged, in a dating relationship) are a social unit with their partner. Both partners should be invited by name on the invitation and it is incredibly rude to just invite half a social unit. Your FBIL and his girlfriend are a social unit. They get invited together.

And if that weren't enough, if he's the BM, he's in the WP. It's good manners to extend plus one invites to a WP members, regardless of whether you are extending that courtesy to other single guests. So by excluding the BM's girlfriend, you would be inviting everyone in the WP to bring their spouse, fiancé/fianceé, bf/gf, or random date except for the BM. You would be expecting him to be the only WP member to show up alone. Again, so rude.

And what everyone is pointing out about this woman possibly being your relative someday if your FBIL ever married her is valid. They've been together 3 years? There's a high chance that means she's not going anywhere. I have a BIL who's wife was standoffish towards me. It has not mattered how friendly I have tried to be or how accepting the rest of DH's family was of me after having dated him for years and then having gotten engaged to him. DH had proposed to me and as the future aunt to her baby, I wasn't even welcome at her baby shower, nor could she accept a friend request from me on Facebook. It seriously took us going through with the wedding for my BIL's wife to decide she could be friends with me on Facebook. Don't be that woman to someone else. You don't have to be her bestie. You don't have to start acting like she's already your SIL. But, be kind. Be inclusive rather than exclusive. Make her want to be nice to you. Someday, you might be stuck with each other.

If you don't give him a plus one, he wont be wanting to get to know you better...

Yes you have to invite her not only to the wedding but to the rehearsal dinner as well

@HelenaHandbasket, I don't think she should be invited to the rehearsal or rehearsal dinner because she doesn't have a part in the wedding.

Of course you have to invite her! You invite all SOs. Also, even if BM were single, you'd have to give him a plus one because he's in the wedding party. If they've been dating for three years, there's a decent chance that he'll marry her. Do you really want to piss both of them off forever by not inviting her?

Yes - you are required to invite her.

@Shanyn-if you are having a rehearsal and a rehearsal dinner you MUST invite the SO's for the dinner. If you don't want them there then you don't have a rehearsal dinner. You don't keep forcing these people away from their SO.

@HelenaHandbasket, they don't need to be invited. Not to the rehearsal when they have no part in the wedding. I do agree that she does needed to be invited to the ceremony and reception.

Shanyn, it would be considered rude to exclude SO's of your bridal party even for the rehearsal dinner. That's a good way to piss people off.

@shanyn-so those that are nearest and dearest are being asked to "practice walking" for you, taking time off work, spending money on attire, gifts and possibly throwing pre wedding parties and then you are telling them that they can't bring their SO to a dinner after???? Don't hold a rehearsal then

Yes, invite her. Don't be rude.

Yes! If your guest is seeing someone then you must invite their significant other. You don't have to socialize with her, but she should get an invite.

Yes

I understand where you are coming from. I also dislike my fiance's brother's girlfriend because she is a cheater and very much uses men for money and has broken up with him before but sadly if he wants her there she has to come. Though I am hoping she won't. She knows I have a low opinion of her.

Yes. This is a no brainer.

If they are in a relationship she is not a plus one. You have to invite her.