I started out "solo" hunting at 13. My little brother was 12. The difference in when we started had to do more with my brother being able to go to his older brother or our father if any problems came up.
It also did not help that my birthday is in the fall. I was not ready for the deer hunt at age 12.
IME age is an arbitrary marker. It all depends on the hunter themselves. It also depends on the support for the new hunters as well. I'm slmost five years older than my brother. That meant I was a relatively experienced hunter by the time he started. I was there to help my little brother as much as I was to get my own deer. Hunting in my family is not about the kill, it's about the camp experience and being there for everyone.
Becoming a good hunter requires patience, time in the field, and positive people there to make the tough times seem unimportant. You should be having fun even when things are not going the best.