Chip on the Shoulder (1960)

Miguel (the new sheriff) and Gumaro (the supposed villain who secretly protects the town) meet when Miguel is hired to bring Gumaro to justice. Instead of arresting him, they become friends. They rid the town of the villains and each one marries a local woman and each couple has a son. Then both couples leave the town to establish lives elsewhere. Years later they are called back for the reading of the last will and testament of the town elder who had hired Miguel. For different reasons, neither one wants to return and each one sends his son in his place. At the same time, both Miguel and Gumaro suspect that their wives were unfaithful because each son resembles the other father. Eventually both fathers and both sons find themselves in the town, where a comedy of mistaken identities ensues.