At what age should a child begin sleeping on their own in their own room?

My husband says that as kids they never saw their parent’s sleeping in the same room, that even if one of the kids awoke at midnight, one of the parents would immediately leave the room. My son is 2 years and 2 months. At what age does the child have to sleep in his own room? Coming from a background like my husband’s, he feels it awkward for the child to sleep in the same room as we do.