How to send an invitation when you're not inviting everyone

Prior to writing the invite, your fiance needs to call him and give a heads up about her not being invited and have that conversation. Not inviting his spouse, but inviting everyone else in the household may cause him to decline all together (regardless if you call or just send the invite). While I agree with the PP, writing out all the names (while the correct way) comes off as you going out of your way to not invite her (because it is. only you two know how bad she is).

On the invitation, only list the names of people invited. But I agree with others - Your fiancé needs to have a conversation with his brother in advance and let him know; the invitation is not the way to do this. And also agree with others that you both need to be emotionally prepared for the entire family to decline, just in case.

Have your FH speak with his brother FIRST so that way it's no surprise by mail. Just be mindful that if the brother stands by his wife's side no matter what then none of them will probably go. And if she is toxic then I'm sure she would be dramatic and cause up some drama. So, just be prepared for that as she may want to bad mouth you guys or whatever it may be :/

Oh yikes, that's a bad situation lol. Honestly I would not send an invite to the house as seeing in writing, that you are purposely excluding her is gonna cause an even bigger drama. I would just have FH verbally say, hey this is when our wedding is, you and your kids can come but not the wife. Bad news is easier to stomach when it doesn't come in the mail in writing to your own home lol