Their child never wins.
Sharing is a beautiful concept, but it’s vague, it has no clear rules: we don’t ask our kids to share, we know they‘ll do it when they are ready.
Instead, we invite them to wait when somebody has a toy they want: this promotes patience. We tell them they don’t need to share their toy, if they don’t want to: this prevents them for feeling possessive and defensive about their own things.
This way, they learnt to share because they want to, not because they have to.