Nov. 8, 2013 at 9:24 AM ET
Johnny Galecki is no kiss-and-tell man: It's been three years since his split with "Big Bang Theory" co-star Kaley Cuoco, and he's just now opening up about their secret relationship.
The good news is they've remained close. "We're dear friends, still," the 38-year-old actor told CBS Watch! magazine in its new issue. "She's not an ex, she's a part of my life."
But the reason this relationship hasn't been talked about more publicly is that the duo kept it secret while it was happening for professional reasons.
"I just don't like to speak about it. And not because I'm trying to be enigmatic; I just worry that it will conflict with people's acceptance of ("BBT" characters) Leonard and Penny.... I get the curiosity, but I don't want to distract from the story."
The duo have appeared together on the hit CBS comedy since 2007, and in 2010 Cuoco told CBS Watch that they had dated for "almost two years."
"It was such a huge part of my life and no one knew about it," she said then. "It was a wonderful relationship, but we never spoke a word about it and never went anywhere together."
The now-27-year-old actress agreed with Galecki at the time that they should be on the QT to help the show. The couple was "so protective of ourselves and the show, and we didn't want anything to ruin that," she said.
But it was that secrecy that contributed to their breakup. "Everyone was always asking, and we deny-deny-denied," she said. "And I'm like, 'Why am I denying this person that I love?'"
The co-stars were able to go on and remain friends, having promised each other that they'd keep it professional if a breakup happened. "I'm so lucky it was a mutual ending and that we don't hate each other," said Cuoco. "We dodged a huge bullet. Dodged a war."
And, they've moved on. Cuoco is now engaged to tennis player Ryan Sweeting. Galecki, whose former girlfriend and "Roseanne" co-star Sara Gilbert made headlines in September by saying their relationship helped her realize she was a lesbian, is now dating actress Kelli Garner.