Well I always thought there was a legal age too. And 12 is the "assumed" age for being able to stay home alone or with younger siblings. But I would have to say that if you have a 12 yr old that acts younger, I would not leave them alone or with any younger children. Luckily, I do have a daughter that is 12.. will be 13 in Feb. And she is a HUGE help to 3 younger siblings. I have 7yr old & 5yr old boys as well as a 2 yr old daughter. And she will babysit so that I can go to grocery store for that long list of groceries that just gets longer. Or so that I can have lunch with her dad, my hubby. I never leave her for more that 2 hours. I think that at christmas I did leave her for almost 3 hours. Because of traffic while I was out Christmas shopping & I was frantic that she was going to pull her hair out. But I kept calling from my cell & they were finger painting and making homemade Christmas card to send out. It was great~ Trying to make this long story short~ I would have to say that you should really ask about the "maturity age" rather than a biological age. I know that I would not want my stepson in NC left alone, which his mom has done for years. But I have to admit , that he is mature & responsible enuff to handle it. I think that I was only looking for a way to be mad at the real mom. But when it came down to it, she was not leaving him because she HAD to, but rather because she knew, as well as myself that he could handle it. Knowing that there were neighbors home helped ease things too. So make sure you are not looking for another way to be mad at actual parent. Cause the child could also think that you got mad about their being left home alone, because you did not trust the child. Thank God I figured it out before I opened my mouth &inserted my foot.