When Merritt Paulson watches his Portland Timbers play, he is always joined in the owner’s box by the team’s general manager, Gavin Wilkinson.

But when the Timbers take on the Columbus Crew on Sunday in Major League Soccer’s championship game, the M.L.S. Cup, Paulson will have extra company: his father, Henry, a former Treasury secretary and a former chairman of Goldman Sachs, and the rest of his family.

Henry Paulson, who spends much of his time these days working at an institute he started after he left government, is no stranger to the Timbers and his son’s work: He helped him buy the club in 2008 and pay the $30 million fee to enter M.L.S. in 2011.

“I’ve been a sports fan, but I never, ever considered investing in a sports team,” the elder Paulson said in perhaps his first interview about the Timbers. But “he had come to me and convinced me with a compelling case that soccer was a great investment, and it has become increasingly clear that he had the capability to do this.”