This is the answer off one of the websites I visited:
Legal Age
The age at which a child can be left at home alone is only legislated in two states, Maryland and Illinois. The legal check is whether or not the child is safe and has the ability to take care of themselves. Most authorities agree that leaving a 12 year old alone at home for an hour or two is acceptable, but they should not be responsible for other children.
_________________________________________
I started babysitting at age 11, but I lived in a small town and looked older than my age. Looking back, I was probably too young. I never had any problems, but I would not hire an 11 year old to watch my kids. If your older son is mature, follows instructions, etc, I would think they would be okay for a short period of time. Try leaving them while you run a 15 minute errand, then kind of build from there.