It's not just a meme. Well, the side-by-side comparison photos of Justin and Fidel are a meme in the widely spread sense. But it is a fact that in April 1971 the Trudeaus were a) in the Caribbean for two weeks and b) did not publish their schedule, including at least one visit to an undisclosed island. Justin was born in December 1971.
Add to that c) the remarkably familiar way Fidel, Pierre, and Margaret acted toward each other in Fidel's first official meeting with them in 1976, and d) Justin's remarkably laudatory statement on Fidel's death.