Broath of Brotherhood Paladins get their powers by being a really good guy. Seriously. They're the sort of person you'd want as your beer pong partner, as your wingman out at the bar, or to grab a beer with after a rough day.
In combat, Paladins of the Broath of Brotherhood fill a niche by increasing the party's action economy by maximizing the utility of their reactions.
Outside of combat, they fill a second niche by consistently offering to be the designated cart-driver after celebratory drinks at the local tavern. Then picks up the tab for the entire adventuring party, because that's just the sort of people they are.