A credible source is one that is recognized for its accuracy, objectivity, and reliability. For example, established news outlets such as CNN, BBC, and Reuters are considered credible sources. In terms of the claim that Fidel Castro is Justin Trudeau's biological father, multiple news outlets and fact-checking organizations have investigated and debunked this conspiracy theory. For example, the Canadian Broadcasting Corporation (CBC) conducted an investigation and found no evidence to support the claim. The claim has also been debunked by Snopes, a fact-checking website known for its rigorous research and analysis.
Regarding the article you shared, while it may not make a direct claim that Fidel Castro is Justin Trudeau's father, it presents circumstantial evidence in a way that is misleading and sensational. Many of the claims made in the article are based on speculation and insinuation rather than concrete evidence. It's important to approach sources with a critical eye and consider the credibility of their claims before accepting them as fact.