Moose and Molly

"Jack will be able to date our neighbor's daughter if her father approves of him" says Molly.
"Father is anxious to meet you!" says the Millers' neighbour to Molly's Brother Jack.
The Millers' neighbour's father waits in a darkened room, standing next to a lounge chair at which two lamps have been pointed, making it the only well-lit spot in the room.

I'm confused. Why does Molly's Brother Jack need the approval of his girlfriend's grandfather?

Moose and Molly, 2013-10-21.