Kristy Swanson

Kristy Swanson and Lloyd Eisler

Last spring, Skating with Celebrities star Lloyd Eisler and his wife, Marcia, were happily anticipating the arrival of their second child, with observers describing them as "such a great couple."

That was then. Now Eisler, the former World Champion pairs skater, is with Kristy Swanson, the actress he partnered with on FOX’s Skating with Celebrities.

As reported in PEOPLE’s new issue, the 42-year-old Eisler - currently separated from the mother of his two children (Seth, 10 weeks, and older brother Ethan, 21 months) - is now openly dating the former Playboy playmate, 36, best known for starring in the 1992 film Buffy the Vampire Slayer.

Says their Skating competitor Bruce Jenner, who saw them at a recent press event: "They seem to be very happy."

According to one source on the set of the show (which premiered in January but taped in the fall), the pair’s away-from-the-rink relationship was an open secret: "Everyone knew there was something going on. It was obvious they were together."

Well, not to everyone. "I just noticed that they got really good (at skating)," Jenner tells PEOPLE. "I never knew anything until I saw it on the news."

As for Marcia, 31, who visited the L.A. set last fall, she "felt a vibe that things weren’t normal," says a friend of Eisler’s. Still, Marcia’s suspicions weren’t confirmed until, she claimed, Swanson forwarded her an e-mail that Eisler had sent her. (Neither Swanson nor Eisler will comment on either the e-mail or their relationship except to say that Eisler’s marriage was over before he started seeing Swanson.)

Marcia confronted her husband, and on Nov. 5, Eisler moved out of his and Marcia’s home in tiny Bath, Ont. (population 1,000), to an apartment in Kingston, 15 miles away. "We became officially separated Nov. 30," says Marcia, who gave birth to Seth two weeks later.

Although the couple have yet to get a divorce, she’s already gone back to her maiden name, Marcia O’Brien, and she’s also changed the children’s last names to hers.

For more on this story, pick up PEOPLE’s latest issue, on newsstands Friday.