My daughter is 4 and she has cleaned her own room for about 2 years now. It used to be with supervision and assistance, but now days she does it herself every night before bed.
10, 7 and 4, and yes they do. I still help my newly 4 year old, even though she can.
DD is 2 and a half. She'll help put her toys away, put clothes away, and make her bed, but doesn't do it on her own. DS is a week and a half, so he doesn't make a mess of his room yet.
My DD is 6 and is supposed to clean her own room. She can do it without help, but usually it entails a LOT of nagging and prodding. It never really gets out of control messy, but when we have company over I like all of her toys to be put away and her clothes (the real problem) in her closet. It takes longer than it should and some reminders, but yes she CAN do it! Haha.