Ron Swanson has mentioned having at least one brother, but for the first time someone is introduced to one of them (Don). In the background we see a couple other guys (Lon and Vaughn) shuffle off after Ron gives the signal to leave.
“We build things. Come on let me show you around. This is a door, and these of course are walls. What else, what else. Ah meet our Vice President Don Swanson. Don this is Andrew and Benjamin.”
“Is this your brother? You have a brother?”
“No. Fine, yes, suppose the cat’s out of the bag. I have a brother.”
(Ron waves two men on the other side of the room away from him)
“All those years together at the Parks Department you never told us you had a brother.”
“You worked at the Parks Department?”