The first two in the OP are definitely 14 or younger, I know for a fact the first one is 14, and the second one I didn't know whether he was 13 or 14, they were both too young to bowl high school this year. The last one is a collegiate bowler, and I believe he's 20.
Dear Gizmo823:
All three of them seem to have good basic form, but at least two of them appear to be more than 14 years of age.