In the game, Bill and Frank's relationship is only alluded to, and they had a falling out. You only see Frank's decomposing corpse in a cut scene after Bill, Joel, and Ellie find him after he had been bitten by an infected.

The dynamic between Bill and Ellie in the game (even though it was brief) was one of my favorite parts. When they announced they had cast Nick Offerman in the role of Bill, I thought he would be great in that role in his interactions with Ellie. I was disappointed that Ellie never meets him in person in the show.