Is friend BU about wedding invitations?

I think for a traditional wedding (other than a really small one) then the exclusion of an established partner or husband is meaningful - at least that's the social convention.

Anna and Brian are of course welcome to invite whoever they want to their wedding without partners, but they should be aware that they are breaking a convention by doing so. If this wasn't the case then Katie and Jessica wouldn't feel hurt in the first place.

Well it's irrelevant because they're not invited.

I'm a bit puzzled by the first line of your OP though...

"I’m a bit stuck between friends."

No you're not.

You've got your invitation and your plus one.

They've got their invitations with no plus one.

You're not stuck between anyone unless you're purposely inserting yourself for the drama.

Life's too short to get upset about it. It's not too short to be entertained by other people's little dramas!

oh! What’s she said about it? Do you suppose she’ll have a re-think or stand firm?

They only make an effort with Brian through gritted teeth though right? They "tolerate" him, you said. It drives you mad how "codependent" they are. You've tried to talk to your friend and get her to leave Brian at home?

Sounds like they're thinking "I have to put up with seeing fucking Brian every time, so the bride should have to spend time against her will with my boyfriend/husband for once [at her own wedding]".

sounds toxic af

I think that Anna is being really rude. Jessica invited her and Brian to her wedding so surely it's just good manners for Anna to to reciprocate.

Anna is using her wedding to punish Jessica and Katie for not insisting that their partners socialise with Brian. Close friends would normally get a plus one invitation but Anna is willing to jeopardise their friendship in order to make a ridiculous point.

Neither Jessica nor Katie’s partners want to socialise as a couple with Anna and Brian. Not because they dislike them, but because they’ve got their own friends and social lives

Sauce for the goose, yeah?

I think it's healthy for a couple to have their own friends and not automatically socialise as couples. I know in an ideal world there would be time for both, but people who are time short probably don't want to forego a drink at the pub for theatre, meal etc with another couple.

I think it is weird to not invite a couple to a wedding but I suspect this has changed over the last decade or so because most people seem to think this is really normal. I've only ever been invited to a wedding without a partner as part of a big group.

I think not inviting partners is really rude. They are established couples not new boyfriends, so should be invited. We invited people to our wedding we’d never met such as dh’s cousins boyfriend. They’re now married and we both went to their wedding.

Sounds like their partners need to get over it then. Weddings aren't about who has the best plus one.

The cost per person is £150 a head + these days. Who wants to have a load of people they never see or socialise with in their photos. Why can't you go as girls?

Well you described it badly then.
It came across as two women who like the bride but aren't keen on the groom (you said they "tolerate" him)
And two partners of those women who have very little do with the bride or groom, certainly aren't friends with them, and probably wouldn't care if they never saw either of them again.

Which two of the B&Gs family or actual friends do you think should be taken off the invite list so the unbothered partners can attend?

Do the women think that because they keep up the pretence of tolerating the groom, the bride should pay they back by pretending their partners are important enough to the B&G to go to the wedding? Even though everyone knows they're not?

I can only assume you're all quite young as honestly life is much too short to give a second thought to this façade of who wins the friendship hierarchy, never mind being "extremely hurt".

Will Anna hear about this upset?

If Jessica and Katie’s partners can’t be arsed socialising with Anna and Brian then why should they get an invite.

I suspect the partners aren’t bothered about the wedding but Jessica and Katie don’t want to go on their own. Tough tits J & K.

If the husband and boyfriend can be bothered to socialize I totally understand why they not invited. Bride and groom can invite who she wants and why pay for someone who not interested in spending time with them...sounds sensible. Also 100 isn't that many but the time you've invited family and close friends of both the bride and groom

I’ve been to several weddings were dh wasn’t invited (and vice versa). Mostly work colleagues but one a childhood friend. My dh was glad not to be invited and I was too. Meant I didn’t have to spend my time keeping him company and I could catch up with friends. I don’t see the big deal.

I think both men would be happy to go to big events - big birthdays, weddings, christenings etc

I bet they would lol with all the free food and entertainment.

However, they'd have to be pretty entitled to expect an invite when they've put none of the socialising leg work in.