To not invite sister to social gathering

Yes the chances are low but it's not fair that the group leader gets to invite an outsider, regardless of the reason, when everyone else isn't allowed

I can see where you're coming from as you'd be put in a difficult position if other members wanted to invite 'outsiders' too and if you weren't the group leader, you'd have to ask the leader if your sister could come and they'd probably say no I'd imagine.

Your mum shouldn't have invited her but I'm also wondering if your sister would even want to go as she's not confident enough to join the actual group.
I'd be suggesting she attends for a week or two now to see what she thinks and then it's not a problem. I mean, you and your mum are there, so it's not like she doesn't know anyone!

Well they might I suppose, but I'd say the odds of multiple group members having a friend or family member who lacks confidence to have joined the group to date and would benefit from a soft introduction of a social would be low. However in the unlikely event of this being the case, the OP could include them too if room, on a first come first served basis.

In hobby group socials it's either group members only, or bring your OH (sister in this case), which totally changes the dynamic because you've got men there and you end up talking about planning regs, IME. Two separate events is the way to go, with DSis invited to the other one.

Social anxiety can be crippling and not something your sister 'chooses', maybe getting her to the Xmas gathering will give her the confidence to join the group in the new year? I'd not stress about it and see it as a good thing. She may well fuck out closer to the time anyway

But other members might be in the same boat too ie have friends or family members who they would like to join but haven't yet but aren't allowed to invite them to the social

The OP has already said that wouldn't be possible due to limited numbers.

My WI group often organises social events and it's the same. You can't just invite someone outside of the group just because they're related to the person in charge

The sister isn’t part of the group.

The social event is for group members only.

None of the members are allowed to bring a plus 1.
It doesn’t matter how lovely their DH’s or friends are, it’s for group members only.

I’ve been to plenty of Xmas work dos where it’s staff only and it’s not a plus 1 event.

The rules need to be the same for everyone.

If people are allowed to bring a guest, then let her come.

If it’s for members only (which it is), then don’t let her come.

It doesn’t matter that she’s family.

You don’t get to break the rules, as that’s not fair on everyone else.

I’m shocked that any of these posters think it should be one rule for you and another rule for everyone else.

I completely agree with you OP.

I can't imagine your thought process. Your sister is lovely, your mum is a part of the group and your very first thought is to create a post about her? How do you go from that to this?

You sound like your biggest beef is that your authority as group leader has been undermined, are you insecure and need to assert yourself, your upset that you you weren’t asked first before your sister was invited feels like it’s the biggest issue for you…

I think you're being a bit jobsworth OP. You want your sister to have friends, join the group and gain confidence. The fact that she's agreed to go on the social is a big step in that direction and may well lead to the outcome you want. Seems daft to be taking umbridge that she's not part of the group (yet) and you're in charge so it was YOUR decision and so forth. Big picture time.

I went to my hobby’s social event last night and plus ones were welcome. But if that isn’t the case with your do then could you maybe compromise and have the meal but then head somewhere for drinks after where partners/plus ones are invited? Might make sense to do it that way around so that you can have hobby chats over dinner and then others join after to broaden out the invitation list and the discussions? It was actually really nice meeting other people’s friends/relations/partners last night as it gave a bit more of a window into everyone’s world outside of our hobby. Was lovely.

Why are you assuming people will have a problem with it?

Maybe they wont. If anyone does, maybe explain you are hoping your sister would join the group but she's shy and this might encourage her to do so?

Most people would see this as a kindness and not be petty, at least I hope so!

It makes perfect sense. If the group was bigger, OP would have booked a bigger table or chosen a different venue. Even now, while it would probably be easy enough to fit in one more person, what happens when the group members start saying, “Oh, well if we can invite non-members, can I book a place for my sister/neighbour/old school friend too?” Suddenly you’ve got to replan the whole thing.

I was going to say if your sister is going you should make it clear to everyone that it's "plus one" and your mum has chosen your sister as her "plus one".

Or, you treat it as a social/prospective new participants meet-up and have a separate Xmas meal for the existing group.

As you've already made the plans I agree be firm with your mum and sister but suggest /organise a "prospective new members social/plus ones" which your sister can come to.

She's much more likely to form friendships doing an activity than just going to a random Xmas meal anyway.

I’m surprised at some of the early replies saying “Awwh, don’t be mean; it’s your sister!” and all this business. Can people really not see how it will come across if the OP, who is running the group, has said no plus ones, but makes an exception to let her mother bring her other daughter? It will start to feel like the OP’s family meal out where she’s graciously letting others attend! (And yes, I DO know her mother is a genuine member of the group. It’s still going to look shit if the group leader’s mother is allowed to bring a guest, but common or garden members can’t.)

OP - hopefully your sister won’t even want to go, given that she doesn’t want to join the group. But I still think you need to put your foot down with your mother. Point out that others in the group may have sisters, cousins, friends etc. who they think would benefit from being a bit more sociable - does that mean they should all be allowed to come along too?

The suggestion from another poster earlier about some more casual “feel free to invite anyone who might fancy trying out the hobby” drinks at a later date is a good one.

Maybe choose a different venue and everyone can invite a ‘+1’ if they want? I’m guessing it would awkward for your sister to know that she’s the only person present who isn’t part of the group..

It would be mean spirited if she wasn't invited to the group, but she is welcome to attend.

Finding this thread somewhat depressing and mean spirited

It's a Christmas meal - Yes
Time of goodwill - yes
She's the OP's sister - also yes
Has she been invited to attend any of the group activities up to this point - yes

Has she attended any of the group activities up to this point - No
If she attended any of the group activities before the Christmas meal could she attend the Christmas meal - YES!!!!!

@NoSourDough - You have two ways to handle this - either you bring your sister along (perhaps under protest) so that she can attend a couple of sessions with this group so that she takes part in the activity and can therefore attend the lunch as a member of the group or you tell your mother and sister that as she is not a member of the group she can't come to the Christmas meal but that as group leader you're going to help organise a meet and greet session and a get to know you session in January (as someone up thread suggested) and she can come to that instead but you can't change the rules to appease your mother or her.

If OP came on here and said a hobby group member wanted to bring their DH, who was not a club member, people would be all over it shouting "changes dynamics". Why should it be different because it's someone's sister?

I used to run an archery club as a hobby, adults and kids as members. When we have a fun shoot for Christmas which included food and Christmas stocking gifts for the kids we would have non club members trying to attend. We were a small club paying for this out of club fees we couldn't afford or even want the hassle of dealing with stragglers just because they thought it would be fun.

But she isn't a member of the group! I suppose if she went to your work lunch, she might decide she wanted to work there; but that's not the way round it works!
I know the examples aren't identical, but it's the same principle.

It is not a work lunch its a village hobby group, a group the Op had encouraged her sister to join, who if invited and meet the others may well feel able to join.

I think being "group leader" has gone to your head OP. You sound like a 6 year old.