My son just turned three. He slept two nights in his twin bed in the room with his older brother. On the third night he wanted to go back to his room and sleep in his baby bed because he could not settle down. He sleeps well in his baby bed and has never climbed out of it. Is it okay to postpone the transition to the big bed? Do you recommend a certain age for this transition? Eventually, we need him to sleep in the room with his brother. The baby-bed room is actually a bonus room that we use as our homeschool room.