I feel a little daft asking this, but wanted clarification!

If you are looking at a will, and a child of the deceased received money/portions on a date years later, have they reached 21?

As far as I can fathom, a 12 and 14 year olds can marry, and leave wills, so I wasn't sure whether 21 would be the date they would go and receive their inheritance.

Can someone clarify the legal side of all this for me?

Thanks Beccy