The Town Went Wild

The Town Went Wild is a 1944 American film directed by Ralph Murphy.

Arriving at the Justice of the Peace, their wedding has to be delayed as state law requires the couple to post banns of marriage in the local newspaper for three days prior to the wedding. Returning to their own town, David prepares the banns to be published as soon as possible and goes to the local town hall to obtain his birth certificate for his government posting. The clerks discover that due to the fathers of Bob and David fighting when the children were born, the two infants were mixed at the hospital with David being a Harrison and Bob being a Conway. Not only is Carol set to marry her brother, but the intention to do so faces a fifteen year prison sentence.

Source: Wikipedia