Piano man Billy Joel married the mother-to-be of his next child in a ceremony Saturday that surprised his Fourth of July guests on his Centre Island estate.

The wedding vows taken by Joel, 66, and Alexis Roderick, 33, were officiated by Gov. Andrew M. Cuomo on Saturday evening at the singer's annual Independence Day party, according to Joel's publicist.

Spokeswoman Claire Mercuri called it a "beautiful wedding" on her Facebook page.

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Joel's daughter, singer-songwriter Alexa Ray, 29, was part of the small group of guests, the publicist said.

This is the first marriage for Roderick, a former senior risk officer for Morgan Stanley in Garden City and an accomplished equestrian. It is Joel's fourth.

The two have been dating since 2009, after meeting in a Huntington restaurant, and are expecting their first child later this summer.

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At Cuomo's request, the State Legislature on June 25 granted him the right to officiate at weddings. He has also presided over two same-sex weddings.

Spokespeople for Cuomo either did not return calls or declined to comment.

Joel has performed at Cuomo fundraisers and added star power to other public events held by the governor over the last four years.

In a recent interview with Newsday, Joel said he was excited about spending time with his new daughter.

"I'm probably going to be able to spend more time with this kid than most people are able to spend with their children, because I don't have a regular job," he said. "I could be a stay-at-home dad for as long as I can stay alive."

The music legend is on tour, with his next sold-out stop at Boston's Fenway Park on July 16.

Centre Island Mayor Lawrence Schmidlapp said he was at a party a quarter-mile away and had no idea the wedding was taking place.

"I'm upset I couldn't marry them," he joked. "I'm here two years in my role and I would love to marry somebody."

With Michael Gormley