After 15 years of marriage, Mariska Hargitay and Peter Hermann are still going strong, thanks to one key ingredient in their partnership: laughter.

“I never thought I would have this much laughter in my life,” says “Younger” star Hermann, 51. “Not just actual laughter, but also the way that Mariska is just the embodiment of laughter, of joy.”

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The couple talk all about their long-term relationship in a new cover story for People magazine. The pair, who met on the set of “Law & Order: SVU” in 2002, are parents to sons August, 12, and Andrew, 7, and daughter Amaya, 8.

The actress reveals she cried after her first date with Hermann.

“As a little girl you’re told, ‘Oh, when it’s the right person, you’ll know.’ But listen, I have been engaged previously and I never knew,” she says. “We went to church together, and it was like getting hit with a lightning bolt, and I just started sobbing. Peter thought I was crying because I was so moved by the service. No, it was because I was just overwhelmed, realizing he was the one.”

Hargitay, 55, who has played Lieutenant Olivia Benson on the fan-favourite series for 20 seasons, says its “not that we don’t fight” in the interview, but laughter has helped them get in tune with one another.

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“It’s the way we find our way back to each other,” Hermann explains. “It’s this fantastically, wonderfully ridiculous way that we can swing back and forth any number of times in any given day. But fundamentally we know we have the same destination.

“We know where we’re headed, and it’s good and we know we’ll get there together.”

Despite their strong bond, the couple don’t plan to renew their wedding vows any time soon.

“[E]very five or 10 years when I ask Peter if I can renew our vows, he says the same thing…” Hargitay says. “I say no,” he interjects. “I meant it the first time.”

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