Prepon told Us Weekly "it's incredible" her two former castmates are now dating seven years after the "That '70s Show" ended. She said she and her costars from the comedy are still close after all these years.
"They're like my family," she said.
Prepon confirmed Kutcher was Kunis' first kiss when the starlet was just 14 years old.
"He was. He was," she said.
"I wasn't surprised either," Prepon said of learning the two were dating in April 2012.
Rumors began circling earlier this month that Kutcher and Kunis are engaged after the actress was spotted what appeared to be an engagement ring. Prepon said she expects to get an invitation to the nuptials should they take place.
"Obviously if people wanted us there, which she would because we're all family -- then of course I would be there," she said. "We support each other no matter what."