My kids are close in age and birthdays are a couple weeks apart. We always combine their birthday party. One big party, more fun and less trouble for us than two smaller parties when a lot of their friends outside of school (church, neighbors, etc) are shared anyway. They are now getting into school age though.
For school classmates, what do you think would be better? Invite that just says the classmate's birthday? Or mention it's the sibling's party too? I see pros and cons to both.
Putting just the classmate's name on the invite is less confusing and people won't feel like they have to bring a gift for a sibling they don't even know. But if someone shows up and the party is two or thre

