When I did Protective Services our state did not have a specific age.
Rule of thumb based on maturity was 12. However, we did not approve of walking in on a 12 year old taking care of younger sibs for extended period of time, say over an hour and having to fix meals.
If child is 12, home alone for an hour or so, knows emergency phones, has an immediate contact in case of problems, (close neighbor, friend etc) we usually felt it was ok.
If child was 12, immature, had no idea what to do when we asked about emergencies, fire, who to call etc. We were concerned and took steps.
Hope this helps.