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OTRC: 'Mad Men' stars engaged: Alexis Bledel to marry Vincent Kartheiser (Pete Campbell)

They were engaged in a secret, steamy romance on "Mad Men" and now they're actually ... engaged.

Vincent Kartheiser, who plays smarmy ad executive Pete Campbell on the AMC 1960s- themed series, and Alexis Bledel, who guest-starred as his mistress, are set to be married. The actor's rep confirmed the news to OTRC.com on Wednesday, March 20, about three weeks before the April 7 premiere of season 6 of "Mad Men."

UPDATE on March 21: Kartheiser talked to OTRC.com at the show's March 20 premiere, saying that he's a "very lucky man" -- Watch the full interview.

This will mark the first marriage for both Kartheiser, 33, and Bledel, who is 31 and rose to fame in her late teens as Rory Gilmore on the show "The Gilmore Girls."

On "Mad Men," Kartheiser's character and Bledel's, a woman named Beth, are both married to other people -- her husband is a commuter on his New York train. Bledel appears in three episodes during season 5, which aired last year. A rep for the show declined to comment about whether or not she will reprise her role on the upcoming season.

The two actors have not announced a wedding date. They attended the 2013 Screen Actors Guild Awards together in January. Bledel was not wearing an engagement ring at the time.

She and Kartheiser reportedly began dating a year ago, according to Us Weekly, which said in June 2012 that the two were spotted kissing on a flight from New York to Los Angeles. The magazine said at the time that they had been going out for several months.

Bledel previously dated her "Gilmore Girls" co-star Milo Ventimiglia for three years. They split in 2006. People magazine, which first reported the news about her engagement, said he was once linked to Rachael Lee Cook. The actress is best known for her role in the 1999 movie "She's All That." A year before the film was released, she and Kartheiser starred in the movie "All I Wanna Do."

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