AIBU to not want to invite sibling a year younger?

[JaggedStone]

Trying to sort out DD birthday (will be 7) in a couple of months and asking DD who she would like to invite and one girl has a sibling who is a year younger and I am sure the mum will ask if she can come? It’s likely to be a party at home due to finances so not a strict cap on numbers but obviously I’m then in charge of more girls.
I don’t particularly want the sibling to attend but am not sure what to say?
Surely it’s unfair for siblings to go to all parties when they haven’t been invited and they then get to go to double the parties.

I’m astonished to read some of these posts. DS2 is 14 and no one ever assumed that younger siblings could come. He had a laser tag party one year and we had to book 20 places. 17 boys in class so I invited 3 younger siblings all only one or two years younger, all of whom we knew. All three mums offered to pay for their place although I assured them it was covered in the group price. All 3 said not to do them a party bag but of course we did.
OP if you think this will happen based on previous behaviour make it clear on the invite and stand guard at the door so no one is just dropped off.

I had one parent at my 6 year olds party ask if a much younger sibling could come (3yo) I just said no sorry you'll need to pay if you want to bring him. In the end someone dropped out the night before so I said he could come as we had paid for the space.

I have children 15 months apart and I have never asked if either of them can go to a party if they are not on the invite, I've turned down invites or asked family or friends to help.

If you are having it at home just write due to space invitee only, we would prefer parents to drop and leave.

Sorry if this has already been posted - imagine inviting one of this lady’s kids to a party 😂

www.buzzfeed.com/alexalisitza/mom-goes-viral-kids-birthday-party-invite

I just say drop offs welcome on the invite. Then I say no sorry, space is limited.

[quote Mellowyellow222]Sorry if this has already been posted - imagine inviting one of this lady’s kids to a party 😂

www.buzzfeed.com/alexalisitza/mom-goes-viral-kids-birthday-party-invite[/quote]
That is outrageous