I have begun my research and so far I have found out that 19 State legislatures have passed anti-nepotism laws. I am still looking for federal law. I will continue searching and also follow this thread for replies.
I do remember that when Bush was running for Prez in 2000, before he named Cheney as his running mate, Sean Hannity was promoting Jeb Bush to be W's running mate.
The law was passed soon after JFK was assassinated; if that's any help.
Sean doesn't always get things right and I don't remember Sean saying that Jeb should be "W"'s VEEP.