They were brought together in the Mets’ ownership group by John Pickett, then the Islanders’ owner, to respond to the team’s auction by the family of Joan Payson. “Fred said, ‘I’d like one percent and Saul will take one percent,’ ” Pickett recalled in a 2011 interview, referring to Saul Katz, Wilpon’s brother-in-law and business partner. “And Nelson agreed, with Fred, probably reluctantly, to be president.”

They were not buddies. They were less symbiotic 50-50 owners than the Tisch and Mara families of the football Giants. And it is possible that they would not have become 50-50 partners in 1986 if Doubleday had been aware of a clause in their original agreement that gave Wilpon the right of first refusal on any sale of the team.

Still, they had enough of a bond — forged as partners, not intimates — for Wilpon to defend Doubleday when Doubleday was quoted making an anti-Semitic remark in “Lords of the Realm,” a 1995 baseball history book by John Helyar. “People that know Nelson,” Wilpon said, “know that’s not the way Nelson feels.”

But they agreed on little, according to various reports over the years. Wilpon wanted a new ballpark. Doubleday wanted to renovate Shea Stadium. They took sides internally, with Doubleday said to be a backer of General Manager Steve Phillips and Wilpon a supporter of Manager Bobby Valentine. They disagreed over a proposed sale of the team to Charles F. Dolan, the head of Cablevision, which did not come fruition, Doubleday said, “because of “Wilpon’s insistence on disproportionate control of the team after a sale.”

Finally, in 2001, Doubleday asked to be bought out. But their split would not be easy.

Doubleday initiated it, and an option in their contract allowed Wilpon to buy his half of the team.

But after failing to agree on a price, they hired an appraiser whose valuation was to be binding. But Doubleday thought that the $391 million valuation was too low. (After subtracting liabilities, Doubleday’s take was going to be $137.9 million.). Doubleday believed the team was worth closer to $500 million.

Wilpon sued Doubleday to force him to accept the appraiser’s price. Instead, Doubleday said that he was the victim of a “sham process” and that Major League Baseball was “in cahoots” with Wilpon, a friend of Commissioner Bud Selig, to let him pay less than market value. Doubleday accused the major leagues of undervaluing franchises, in part by manufacturing phantom losses, to fit their labor-relations strategy.