This is very old information but when I lived in California growing up there were laws about this but they only applied to RENTAL properties. If you are a renter, try contacting your landlord or property manager. If I remember correctly, it was a law that fell under whatever the Department of Child Services is called in California. So that would be who I would call to find out the current laws. I don't recall what the ages were, but I am pretty sure that school age children had to be in separate rooms.
Edit to add:
I said law, but actually, thinking about it, I don't know that it was a law, or just a guideline or something of that sort. The reason I even heard about was because a friend in school had an issue with this in their family, and it had something to do with social services visit. They were making them get a bigger apartment because of a custody issue and social services got involved and said they had to. So all of that does not amount to a law, necessarily.