I've got 3 DC, they're 8, 7 and 3.8. I've noticed that in any combination of 2 they get on like a house on fire but in a 3 there is fighting, bickering and 'muuuuuum, he/she (insert crime here)...'
Is it because three is always a crowd? I'm aware that this phase may pass but it's been going on a while and I'm starting to wonder whether it won't!