If true, it's likely that CIA operatives were tasked with getting information from the Castro brothers, as would be the norm for them at the time (re. Russia &c), and it's possible the Castro brothers were at some point helpful.

What most poeple don't seem to understand is the the CIA doesn't plan its own missions, but takes its orders directly from the Executive branch and a Senate committee. The Soviet-Cuba alliance began when Fidel's revolution succeeded in 1959. This obviously made the Castros potential enemies of the US. The CIA, NSA, and FBI, among other agencies, developed their connections with one of Chicago mafia families at this time, because they also knew a lot about Cuba and how to arrange assassinations without the appearance of US involvement. So - Johnson and members of the US govenment, CIA, members of Mafia, &c were already arranging assassinations, and had a good list of snipers and arrangements to put in place in 1963. There was no other reasonable motive for sniper who shot Kennedy.