I suppose Leonard Bonamassa (?!)
Your first guess was best. You deleted the post and left the wrong one. Oh well! It's ok!
OK, you have 1/2 of the question correct for half credit. Good job. His paternal grandfather is Leonard (Lenny) Bonamassa, Sr.
Even if anyone can come up with his maternal grandfather you'll get to ask next.
Rock ON & Keep The Faith,
"He still doesn't charge for mistakes!
"Everybody wants ta get inta the act!"
“Now, this isn’t your ordinary party crowd, here. I mean, there are professionals in here.”