Mine were happy sharing a room way longer than I expected them to. Until DD was 13 and DS was 10.

As long as you want/need them to. We live in an area where most families live in 2BR homes, so if they have more than one kid, the kids share a room regardless of gender. Some have three kids sharing a room, and it works out fine.

My 2.5yo DD will ultimately be sharing her room with her baby brother for as long as possible. We're in a fairly small apt in NYC and it's not uncommon, as another pp noted. I'm hoping they can tolerate the setup for a very long time (college, ideally!) Otherwise we're planning to carve out a truly tiny 3rd bedroom from our living room. We love our apartment otherwise and I'm reluctant to move unless totally necessary! I'll admit I was sort of hoping for a 2nd girl to avoid this conflict, but knowing other families have made it work is always reassuring.

Thank you for the responses!

Kids who grow up in New York City share with their siblings until the oldest goes off to college. If it has to work, it will work.

Mine shared for a year when ds was 6/7 and dd was 3/4 and it was fine. They are now 9 and 6 and dd will occasionally sleep in ds’s room and it’s still okay.

My son and daughter shared a room on and off until DS was 13 and started going to bed later than his younger sister. Otherwise they were perfectly happy sharing a room.

We have a two-bedroom with a boy (age 4) and a baby girl (age 6 months). DS loves the baby and is happy to share a room with her. We are saving for a bigger house. How long can they share a room?