Matt Katz and Aaron Lafrenz of Brooklyn, N.Y., were surprised to receive a letter from President Barack Obama congratulating them on their marriage. (Courtesy Matt Katz)

A gay couple in Brooklyn, N.Y., were surprised to find a letter in their mailbox six months after their wedding congratulating them, but they were more surprised to find it was from the commander in chief.

Matt Katz, 32, and Aaron Lafrenz, 36, were married at the Katz family's Brooklyn home on July 23, 2011, the day before gay marriage became legal in New York state. The following day, the two went to Brooklyn borough hall and were among the first gay couples to legally be married in the state.

This December, Katz and Lafrenz received a letter in their mailbox with the White House seal indented in the paper and the signature of one Barack Obama on the bottom. Obama has been opposed to gay marriage in the past, though he has recently said his views on the topic are "evolving."

Katz told ABC News today that a family friend, Arlene Weinstock, had requested the letter on their behalf after hearing that the White House would take requests upon the passage of the New York gay marriage bill. Weinstock, of Long Beach, Calif., assumed that the request had not been fulfilled when the couple hadn't heard from the White House during the summer, but realized today that she was the cause of the mysterious presidential salutation.

"I was so super confused," Katz said, noting that he was not a major political activist and had no strong ties to gay rights groups. "But Aunt Arlene called me up and said, 'This is my fault!'"

The White House confirmed to ABC News that they sent the letter.

The letter reads, in part, "Your union marks the beginning of a lifelong partnership as you share in the joys of your life together. I wish you the very best as you embark on your journey together and hope your bond grows stronger with each passing year."

Katz said he was happy to receive the letter, but acknowledged the president is probably looking to shore up the gay vote ahead of the 2012 election.

"I do think he's trying to (pander), but I don't blame him," Katz said. "At this point, this is not necessarily a ploy but he can't for public office reasons be on one side, so maybe this is his way of winking at the gay public in New York and saying I really need your vote now."

Katz said his father is a longtime supporter of Brooklyn Borough President Marty Markowitz, and when he first received the Obama letter, he asked his father whether that had anything to do with it. His father said no.

The White House, when asked about the letter today, responded that it "regularly sends congratulatory messages from the president to members of the public."

Richard Socarides, a former adviser to Bill Clinton  and current president of Equality Matters, a gay rights group, agreed that it a fairly normal move and did not signal a change in the president's position on gay marriage rights.

"Those letters usually come out of the staff secretary's office. They're very careful, but I'm sure that - I don't think this is reflective of a policy decision. I think it's sort of curious, but likely serendipitous," Socarides said.

Despite telling ABC News in October that the issue of gay marriage was something he "struggled with," Obama has never come out in support of gay marriage. He has said he supports "strong civil unions." Obama also led the repeal of the military's "don't ask, don't tell" policy, which banned gays from serving openly in the military.

Katz said that despite the letter's mysterious arrival, the couple was happy to receive it and will likely frame and display the letter in their home.

"For a minute there I really really thought it was a gag gift, but it has the seal, and it's him and Michelle. We'll definitely frame it," he said.