While I am certainly not denying the possibility that Fidel is Trudeau’s dad there is another factor to consider. Trudeau’s official father has a bizarre close physical similarity to Fidel, when they were both young:
They look similar, but it should be simple to get some DNA and check it against a Castro.
If the cia,mossad,mss,fis,mi5,random billionaires have not done it a long time ago I would be shocked