Where did the king and duke get their plan about being the Wilks brothers?

The king and the Duke get their plan to pretend to be the Wilks brothers when they meet the Reverend Elexander Blodgett. He knows the Wilks brothers, and in talking with the King and Duke, inadvertently reveals all the details they need to know to in order to pull off a great impersonation of the Wilks brothers.

The king and duke learn that Peter Wilks has died and left his estate to his brothers, from a young man traveling from the town. The boy also tells them that noone knows anything about the Wilks brothers. As the boy is leaving, they realize they can take the identities since the boy will not be around to rat them out.