Kit-Kat:

I don't know about boyfriends and girlfriends, but having a sit-down dinner party and inviting only one half of a married couple (or the equivalent) is really strange and kind of rude. If you want to see just your old friends, organize an informal reunion at a bar or coffeeshop or something. Have a cocktail party/game watch/movie night/whatever and invite everyone over. If you really want to have dinner parties, have half of the group at a time.

Also, if you want to stay good friends with your former buddies, you'd better be on good terms with their spouses or SOs, and snubbing them intentionally is not going to get you there. I'm cool with my husband catching up with an old friend without me, but if that old friend kept issuing invites that excluded me, I'd be less cool with it. You and your friends are growing up and your lives are changing--you need to find ways to stay connected that admit of some flexibility towards that fact.

Plus, it's a chance to expand your social circle--you might actually like some of the SOs, or they might end up introducing you to other people that you might like.

This is the most ridiculous thing I have ever read.

married couples are somehow different than couples who aren't married?

it would be fun to host half the group at a time?

sitting down to dinner requires that the person you are romantically involved with be sitting next to you, but other types of events are fine to go alone?

it's a "snub" not to invite people who aren't part of a group, that you don't even know well, to an event they really have nothing to do with when you don't have space for them?

Come on, do you realize who stupid all of that sounds? The LW doesn't have a problem with anyone's partners, she just can't invite them this one time. and there's no reason they have to be there.