When our sons were younger, they usually played quite well together -- whether it was building forts, playing with GI Joe's, riding their bikes or constructing castles with LEGOS, they were together more often than not. On those occasions when they were being selfish or cranky, bickering and tattling, I stepped in.
"Go to your own rooms and shut the doors. No talking through the walls, no looking out your doors. You cannot speak to each other for one hour."
Lest you think I was a complete ogre, they were allowed to read or play quietly on their own.
This accomplished two things. The innocent one (if there was an innocent) got some relief and a bit of time to play alone! It also served as a bit of reverse psychology. Knowing they could NOT be together made them WANT to be together more than anything! Ah, the fickle heart.
I could hear them (even through closed doors) heaving these long sighs and knew the reality had set in. They were thinking deep thoughts and probably mulling over the wisdom of being nice to each other. Maybe having a brother wasn't so bad after all... they needed each other, right? Good biking buddies, fort builders, game partners, and more.
Who knows ... maybe they were just thinking they didn't need each other as much as they needed one another's share of the LEGOS, Lincoln Logs or GI Joe's.
Whatever was going on in their little heads, the separation solution worked wonders. At least once during the hour, I was summoned by one or the other (or both.)
"How much longer?"
"You've still got 25 minutes until the timer dings."
More long sighs ... and occasionally, a muttering complaint about how stupid they had been to argue. When the timer in the kitchen finally dinged, both boys exploded out of their rooms and grabbed one another in a bear hug.
"C'mon, bubby! Bring your GI Joe's over to my room ..."
"Yeah, and we can build a big fort to put 'em in!"
... Sweet music to a mother's ears. I guess the saying "Absence makes the heart grow fonder" really is true - or, rephrased, "Separation from your brother when you wanna borrow his GI Joe's is almost unbearable."