Different cultures have varying customs on when children should have a regular bed of their own. Intact families are left to their own choices on this usually without interference from the state. The issue becomes critical when a mother in a custody dispute  enmeshes  her children by keeping them in her bed. I call that an aspect of emotional incest on the part of the mother against the children. It is rare but welcome that a judge would act  on this.

http://www.telegraph.co.uk/news/2017/02/12/mother-allowed-two-boys-sleep-bed-has-taken-family-court-judge/