Are movies sometimes made to deliberately bring out the mathematicians and/or gamblers inside us? In the good old days, when a Xerox copy (okay, photocopy - pardon us all over the place) of the hero showed up, the probability that a flashback would reveal that they were separated at some mela or IT job fair, was approximately the same as the odds that, well, Pakistan would beat Ireland.
But cinema is a field of glorious uncertainties, and sometimes the impossible does happen. You end up with two characters that look and sound exactly alike, but have no genetic connections....