Elyssa Geer, an expert in early childhood studies, said the milestone for being able to understand the concept of sharing really happens somewhere around 3 and a half to 4 years old.
It's around this age that kids start understanding that others don't have the same thoughts they do.
So if a child under 4 is sharing, or isn't, Geer says not to worry.
All children learn at different paces, and there's always a chance to model social and emotional behavior for kids yourself.