I have read that apparently children wanting to eat from a parent's plate is a safety adaptation. If mum and dad are eating it, it must be safe, and therefore good to eat! Really, there are far more serious things to worry about.
Back in the Middle Ages, I believe people commonly shared a "plate" (more commonly a trencher, a large piece of stale bread that served as a plate) and a cup between two people at a meal.
New house and a sloping garden
Lasr two letters continued Jan 24