He can't be related to Jimmy. Otherwise Jimmy T. wouldn't be surprised to meet him in Smooth Moves. Jimmy seems to keep in touch with his family quite well.
They probably are just doppelgangers of each other. I mean that's pretty much the whole joke.
Almost like a Hyrule/Lorule equivalent. Or light world/dark world.
He is jimmy's long lost tenth cousin twice removed. or maybe he's just some random fan of his who became so obsessed with him, he practiaclly became him.
Beats me.
I think it's just an amazing coincidence that there is someone who looks and acts just like Jimmy T. It's so silly. But in the world of WarioWare having something like that happen makes sense.