Folk speech–riddle

My source told me this riddle one night after a discussion of the riddles in The Hobbit by J.R.R. Tolkien when we were trying to think up riddles of our own. She said that this riddle was one that her dad told her when she was about twelve. “It isn’t a very complex riddle, but I like it anyway,” she told me. “It’s one of those things where after you hear the answer, you’re mad at yourself for not getting it because of how easy and obvious it is.”

“The first man was in a car accident and was sent to the hospital, where he was in critical condition. When the second man came to see him, a nurse stopped the second man and told him that only family members were allowed to visit patients. ‘Are you a family member?’ the nurse asked. He answered with the following:

‘Brothers and sisters I have none,

But this man’s father is my father’s son.’

Do the nurses allow him in?”

Answer: Yes. The second man is the first man’s father, so he is allowed in.

I definitely had the same reaction that my informant described in her analysis of the riddle. I couldn’t get the answer, and after five minutes of wracking my brain trying to think of something that would make sense in this context, I still wasn’t able to think of anything and was getting increasingly frustrated. Once she told me the answer, I just felt stupid for not seeing it in the first place. This can be categorized as an “enigma riddle,” one that relies on flowery language to confuse the listener. It takes a careful thinker to see the answer to this riddle straight off, and I found that frustrating.