Rehearsal dinner guest lists with uneven family members

No. Dont invite his extended family. Unless your Cousins are under 16 and can't drive themselves, I don't even think your aunt and uncle should come. They aren't in the wedding. And don't cut plus ones. Would you want to go to dinner without your SO?

Don't ever separate a couple. EVER. It's inconsiderate, it's rude, it's against etiquette, it's something that will earn you a side-eye from most people. That's life advice.

As for the dinner, I get why your aunt and uncle are invited, because their girls who are in the wedding are young. But why do you need to invite his aunt and uncle?

I was in my cousins wedding but my parents weren't invited to the rehearsal lunch. I don't think you need to invite your aunt and uncle just because your cousins are bridesmaids.

I think my parents would be angry if the aunt and uncle didn't get invited (and both sets of parents are splitting the bill). On that note, I also figured that since the rehearsal dinner now looks like I get to have 4 additional extended family members, his side should be able to as well? He's got two local aunts, an uncle, and two cousins. No one's spoken about this yet -- my FI and I were both just trying to establish a plus one rule for the wedding and I just now realized THIS issue.

Also the plus one's at the rehearsal -- 4 of the attendants are getting plus ones but are not in relationships, and likely will be bringing random dates. The other attendants who are married/living together of course should bring their partners. But the random dates? If our wedding is local for the whole bridal party, two days before the wedding, in the middle of the week and doesn't necessitate a hotel?

Don't separate couples and don't invite cousins who aren't in the wedding.

I totally understand where you are coming from. My FHs family is small and super close. His three first cousins are in the bp (2bm and 1 gm). We are inviting his two aunts and two uncles to the RD. My parents wanted us to invite my aunts and uncles (without their kids) to the RD also, but then that adds 6 people that I'm not particularly close with. We finally just decided to do BP with SOs, my parents, our grandmothers and his 2 aunts and 2 uncles.

I would say invite your aunt and uncle, but not his.

No extended family unless in the ceremony or with minors. Period. Sides don't have to be even.

What about the random dates?

Who cares about even numbers at a RD? Never heard of this before.

If they get a plus one for the wedding, I think the courtesy should be extended for the rehearsal, BUT I doubt most of those plus ones will attend.

Couples should be invited together. Plus ones who are attending the wedding should be invited to the RD. If these BMs aren't bringing a plus one to the wedding, then you don't need to invite them with one to the RD. Aunts and uncles should only be coming if their minor children are in the wedding. Your cousins in the wedding are young (I assume minors?), so their parents should come. There's no reason for other aunts and uncles to come.