Preschoolers sleeping in the same room can be sweet, but when siblings get bigger and start to crave privacy, things can go sour -- especially if, say, one kid's a neatnik and the other's a slob. Ways to keep the peace:
Start over. Redecorate and rearrange from scratch, with input from both kids. No need to make a big investment-painting the room a color they both agree on and letting them decide where they want to put their beds can go a long way. If there's room, separate the bunk beds so each child can have his own sleeping area.
Give them privacy. Let each child schedule a period of time to be alone in the room each day. A ground rule: Anyone who disturbs his sibling during reserved time loses a block of his own. If space allows, you can also rig a curtain between the beds that can be opened when the kids want to be together and closed when they don't.
Lay down the laws. Have your kids -- together -- create a list of bedroom rules and consequences for breaking them. For instance, they can agree not to borrow each other's clothes and toys without asking, and allow their sibling to pick something to "borrow" back if he violates the rule. Have them post their rules on the door as a reminder.
Get them organized. Designate specific drawers, bookshelves, and closet space for each child. Then set a specific time of day when both Felix Unger and Oscar Madison will be responsible for neatening up -- making beds, tossing dirty clothes in the hamper, putting away books, toys, and art supplies.