Mariska Hargitay and her husband Peter Hermann have been married for 16 years — but there was a moment early on when the actress wasn’t sure it would work out, her Law & Order: SVU costar Christopher Meloni says.

Meloni, 59, had a front-row seat as Hargitay, 57, found love with Hermann, whom she first met when he landed a guest-starring role on SVU. The couple wed in 2004 and are now parents to August, 14, and Amaya and Andrew, both 9.

“This is the Peter story, from my perspective,” Meloni tells PEOPLE in this week’s cover story. “He’s on the show as a guest actor, and I’m looking at her, looking at him, and I’m seeing how she’s acting, right? I know her, and I’m like, ‘Oh boy. Here we go.’ And she’s just, ‘Tee-hee, tee-hee, I don’t even care about him or anything like that.’”

“I just thought, ‘Oh my God, it’s like I’m back in high school, or even grade school,’” he continues. “Sure enough, they start dating.”

But one day, says Meloni, who played detective Elliot Stabler opposite Hargitay’s Olivia Benson for the first 12 seasons of SVU, Hargitay came to set “sobbing” over her relationship with Hermann, 53.

“After they’d been dating a long time, she came in one day and she was crushed,” Meloni recalls. “She goes, ‘Peter and I had a really deep, long conversation. We cried, and I just don’t think it’s going to work.’ And she’s sobbing, and the whole time, the [thought] bubble in my head was just: ‘You’ll be married within five months.’ That’s all I was thinking. I knew. I knew.”

Hargitay also bore witness to Meloni’s major life milestones over the years. When the actor welcomed daughter Sophia in 2001, he and wife Sherman Williams, 61, asked Hargitay to be her godmother. (The couple later also had a son, Dante, now 17.)

“The birth of his first child and being privy to his amazing, solid relationship with his wife, before I had that for myself — I think that Chris and Sherman played a really big role for me, to see this really stable couple that loved each other,” Hargitay says.

“And it made me feel even safer with him, as opposed to: ‘Great guy—but single.’ Or ‘Great guy — except for his romantic life.’ Instead, he’s this man who is as solid as a rock, and who is that rock in his relationship,” she adds. “And I got to lean on it when I needed to. It was like family.”

After Meloni abruptly left the show in 2011 after contract negotiations fell apart, Hargitay continued playing Benson and in 2019, SVU became the longest-running drama series in TV history.

Hargitay was “devastated” by his departure, though the pair remained close as ever.

That connection has never been more apparent than when the two began filming again for Law & Order: Organized Crime, a new spinoff premiering April 1 that features Stabler as the central character.

“It was Pavlovian: Ring that bell, and you get right into Stabler and Benson,” says Meloni.