When you hear about somebody new in the news with the surname of famous person they are usually related to them, so much so that is standard journalistic practice to often state it when they are not related to a famous person. The only people this axiom doesn't work with are people with relatively common names.
Examples include Alan and Robin Thicke, Mika and Zbignew Brzezinski , David and Rush Limbaugh, Chris and Mike Wallace, Steve R. McQueen and Steve McQueen, Julian and Andrew Lloyd Webber, Charlie and Martin Sheen, The Udall family, Jerry and Ben Stiller, Nick and George Clooney, Lucian and Anna Freud and numerous others.
An example where it isn't true is Brandi Chastain and Jessica Chastain. Another example if Mark Hamill and Pete Hamill. The Hamill's and the Chastain's are not releated.
(Originally published July 6, 2012.)