Do you just accept or decline invitations from family or do you ask if you can bring someone or have a conversation about occasion?

Having read the updates, I think YABU to invite others / ask for food for someone who wasn't coming. BUT slagging you off in the manner they did was also unreasonable and unnecessary, they should just have a direct conversation about their expectations rather than getting het up and making snide/unkind remarks.

Eta I have a good relationship with my family so we would just have a normal conversation, people can ask and boundaries can be set without anyone getting upset so do wonder if there's something about you view the relationship.

I think if it’s a specific would you and and DH like to come to dinner Friday night then it’s literally you and DH no kids etc, so you decide if you’re willing to get a babysitter. If it’s would you all like to come for Sunday lunch I’d assume you, DH and any children that live with you. If you have other people visiting say a granny from the other side of the family I would just decline and say sorry we already have guests can we arrange another weekend.
In this instance I’m assuming that you said it would just be you and DH then on the day your husband popped off to get your son and then you asked for a sandwich which was kinda rude once they’d finished. You should have told them beforehand that DH would pop to get son and then he should have picked him up a meal deal/ McDonald’s on the way not expected SIL to start preparing food again!!

Would you really say "regretfully decline" to your own child or sibling? What about "I'm seeing X that day - is it OK if i bring them?"

It depends. If someone was staying with me I'd say X will be with me is it ok if they can come too.? If it was my partner and young children I'd assume they were invited too . I would never assume a dog was welcome.

It all sounds a bit formal tbh. We have a family group WhatsApp chat that has my parents, siblings, a few of the partners and now adult children. Invites will normally go out on there and collect a bunch of ‘sorry we can’t make it’ or ‘cool, see you there!’ replies. Smaller catch ups are normally arranged over text or in person

if SIL is in the habit of inviting specific people, then you phone and want to add others, that irritates her so don't do it now you know.

tbh i would be annoyed too if you said "yes me, DH and one DS are coming" then half way through you go "just off to get the other DS, pls make a sandwich"

It's a pity your mum overheard, but that's what happens sometimes.

in My family it would be a very unusual event that required a typed invitation. - A big party or a wedding might have a fancy invitation but otherwise it would be on a group chat. I would definitely ask if I could bring my partner/step child/dessert/salads etc. Most of our gatherings are informal, everyone is welcome type events.

If I am hosting I need to know how many people Im feeding, additional people at short notice is a pain. However my mother will feed anyone who comes in the door and there is never an issue. So its all in personal hosting styles really.

Word processor! I haven't seen that term since the late 80's. Anyway, I would always ask the host if I could bring another "fucker" with me, but prepared to accept that this might be impractical.

I think it’s the late notice.

‘she said something like then on the day when you’re cooking, the phone calls start’

From the OP ^^

My family is like yours - big family and all very casual. We'll get a text invite generally and a couple of days before it tends to be the host confirms numbers with a casual 'how many do you reckon from your side?' .e.g. we are a family of 4 but 2 adults 2 teens so work shift patterns etc means this often changes. I may sometimes respond with 'think it will be 3 of us but if DS shift finishes early he may pop in for a bit'. That would be absolutely fine. If he turned up at 4pm after the 1pm lunch as in your example, then generally he would be offered a plate from what was leftover. No issues. It would also be a case of 'host, can I bring anything on Saturday' - 'yes please, sibling 1 could you bring a pudding, sibling 2 can you bring a salad etc etc'. This is really normal for us, I didn't realise this was considered strange!

It would generally be obvious if the invitation was for us as a family or me as an individual. If it’s at Christmas or Easter or my birthday, yes, it would always be for us as a family. Generally, we don’t really see family except as a unit (none of us like each other that much 😂). If it was, say, friends though, we do make it clear if we want to get together with the kids or we want to just have adult time to chat. It’s fine to clarify who is invited. It’s rude to ask to bring extra people or turn up with them last minute.

I think that is a bit crazy but now you know this about your SIL you can decide when she invites you places she just means you and you can either say yes for just you, or no if you are with others/ “sorry SIL I have partner and kid here today so won’t be able to make it”. then she can say “oh bring them too” or “that’s too bad see you next time”

It sounds like a difference in expectations; either SIL has been treating the family's (many) requests as demands and not saying a very reasonable "no" whenever appropriate or your brother has been accommodating family requests without checking with SIL. Either way, her annoyance at individual instances has snowballed into major frustration. And if she's accurate that these extra people are being added at the last minute rather than as part of the conversation when accepting or declining the invitation, she has a point.

For me personally, I'd not ask to bring an uninvited guest as a matter of course BUT I might explain why I couldn't go if it were purely logistical (Granny is staying with me that week and I can't leave her alone). That is not intended to force an invite for Granny, just to explain why I declined although it also gives the host a chance to say "oh, bring Granny!" if they'd like to see her/don't mind. I'd do this as soon as possible after receiving the invitation. If plans change last minute and Granny's with me on the day due to an emergency, I'd tell the host this and again if the host said bring her then great, if not no problem but at least they know why I changed plans last minute. These would be rare exceptions, though, not every time I was invited somewhere!!

It's a classic mismatch of assumptions. Doesn't anyone just talk to one another, you know rather than making assumptions just ask.

Mind you I never made it invites sent to my parents despite living alone for 13 years at that point. And my family are weird a close relative married abroad and had a party on return I had to ask to meet the spouse just before I left the party. But I'm still classed as the weird one.

Just decline in future. It's not nice to be thought of as 'flipping hard work' by anyone. So don't go, then you're no work at all.

In my family there wouldn't need to be a question about partners or children coming, they'd automatically be included in the invite so it would just be accept or decline.

I’m wondering if the word processed invitations with names on are an attempt to try and stop unexpected guests, due to prior experiences

Team SIL

They are applications not processors

No, ‘she said something like then on the day when you’re cooking, the phone calls start’ according to you.

That is pretty annoying tbf.

Perfect. X

Who on earth uses a word processor in this day and age. They went out with the last century surely?

anyway no,you don’t just invite lots of people, or bring people uninvited on the day. If you wish to bring others phone or text well in advance, and say I can’t make it, I will bf with x and y. If you wish to invite them just say if not, maybe next time. Or you go alone. But you don’t ask to bring lots of extras each time

I would assume my husband and kids were invited to things like Christmas/Easter/BBQ/ birthday. They’re my family and my sisters brother in law and nephews/nieces. But we are family - if it was my mums new boyfriend I’d expect her to check if he was invited.

I would assume partner was invited.
I would ask about partner’s child but expect the invitation to be extended.
Similarly, I would let them know if I had Granny staying with me, but expect the invitation to be extended.
I would not normally feel the need for a conversation about it otherwise.