I don't think this holds any water. Plenty of orphan children. Also, my parents are alive and I firmly count myself in the adult camp.

Like the article, I think much of what makes you an adult is taking responsibility. For some, the first time that happens may be when their parents die I suppose.

By this metric my uncle, who died in his 70s, never became an adult. My grandmother lived to 93.

Not a happy definition, but at least a clear and consistent one.