Inviting people to rehearsal dinner

Zazulak

We're having a rehearsal dinner the night before our wedding, My parents and IL's are both paying for it, and my mom is organizing it.

Mom wants to keep it to WP and parents only. Mom thinks that our best man's wife shouldn't come, nor should my SIL's husband and their young son, who is our RB.

She thinks if we invite them, we should invite my other siblings who aren't part of the WP.

I think that it would be rude not to invite them, especially since my nephew is the RB, and our best man and wife will be coming from 18 hours away.

Can we invite them without inviting my brothers? What is right in this situation? 

Avion22

Significant Others DEFINITELY need to be invited, as do parents of any kids in your wedding party.  You don't HAVE to invite anyone else who isn't in the wedding party, but honestly I don't know why you wouldn't want your own siblings there.

aurianna

A married couple (or engaged couple or an exclusive dating couple) are a social unit. It's rude to invite one to any event and not the other.

Let your mother know you don't need to invite non-wedding party members, as inviting the wife and husband isn't the same as inviting a non-wedding party member; it's inviting the other half of the social unit. (so inviting the spouses does not require you to then invite brothers not part of the WP)

EDIT
Oh, and if you expect the RB at the rehearsal you should DEFINITELY invite both him and his parents to the RD.

kaos16

Please invite the SO of members of your wedding party. . . to do otherwise is rude.  My fiance is a groomsman in a close friend's wedding and I wasn't invited to the rehearsal dinner. . . . obviously it's the Bride and Groom's choice to make in the end, but I felt slighted by it and my fiance is now planning to not attend the rehearsal because of it.  Hopefully an extra person or two won't break your budget, because really it's the right thing to do!