I recently uncovered a document in my local county courthouse (Lackawanna County, PA) from the Orphan's Court. My great uncle received permission from his uncle to join the Navy. But he was 19 in 1942, I thought that an 18 year old could join the military without permission. Why would he have needed this?
Also interestingly, my uncle needed an uncle to sign this document because his parents were both dead. However, as far as I can tell, the document was signed by an older cousin apparently posing as an uncle. Not that this surprises me; I've heard plenty of stories of young men lying to enlist during WWII.