You're invited! ... but your little brother is not.
This has come up recently in our household. In planning in the invite list for a party, there was one child invited, but her sister not. It was a bit awkward, as the sibling isn't too much younger and really often blends with all the other kids. But, the celebrant was adamant.
It came up again recently, when a friend relayed that his child was inviting an older sibling, but not the younger. So, it begs some questions: what to do when the kids start deciding who to invite and not to invite to parties when it carves lines between siblings? Do parents require their kids to invite kids that the celebrant themselves don't want to invite because of various reasons?