The Beverly Hillbillies is purely fictional. It was developed by writers and producers to bring comedic situations and characters to the screen. There's no real-life basis for the show's plot or characters.
Since this is a fanfiction, the identity of Jethro's nephew could be completely up to the writer. He could be an ordinary Muggle who has some special connection to the wizarding world through Jethro. Or he could be a character with some hidden magical abilities that even he doesn't know about until Harry Potter discovers him.
Yes, it could be. In fanfiction, there can be all kinds of creative interpretations. Maybe Jethro has a deep admiration for Merlin within the context of a particular fan - created story. It might be that the writer has crafted a scenario where Jethro is drawn to Merlin's magic, his character traits like his wisdom or his heroism.
One common hillbillies scary story is about the haunted cabin in the woods. Legend has it that a long - ago hillbilly family was brutally murdered there, and ever since, strange noises come from the cabin at night. People who've passed by claim to have seen shadowy figures in the windows.
The isolation in hillbillies scary stories is often very scary. Since they usually take place in remote areas like deep in the woods or on a lonely mountain. It gives a feeling that no one can come to help if something bad happens.
Well, once my hillbilly uncle thought a bidet was a drinking fountain at a fancy hotel. He put his mouth right under it and got a big surprise when the water sprayed out. It was so embarrassing but also hilarious.