Yes castro knew.He knew the CIA killed Kennedy and knew they tried to kill him many times.Its obvious he knew that the CIA killed him because after his assassination he told an aide of kennedys that was visiting with him on behalf of Kennedy who was trying to establish peaceful relations with Cuba,he said something like-This is terrible,this changes everything. I will have to find out exactly what it was he said but thats pretty close.he said that in a book here everybody should read called JFK AND THE UNSPEAKABLE,why he was killed and why it still matters.That book has overwhelming evidence in it as any open minded and objective person not in denial,can see that the CIA killed him. Castro was a prophet because it did change everything.after his assassination,he tried many times to communicate with Johnson on continuing what JFK started on trying to establish peaceful relations but Johnson ignored him everytime and never got back to him.