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'Mad Men' co-stars Alexis Bledel and Vincent Kartheiser engaged

Their "Mad Men" characters had an ill-fated affair, but off-camera, Alexis Bledel and Vincent Kartheiser are excitedly celebrating their engagement, Bledel's rep confirms exclusively to Us Weekly. "They couldn't be happier," says a pal of the "Gilmore Girls" alum, 31, and Kartheiser, 33.PHOTOS: Costar couplesLast June, Us broke news that the twosome -- Bledel played the mentally imbalanced mistres
Vincent Kartheiser and Alexis Bledel at the Screen Actors Guild Awards in Los Angeles.
Vincent Kartheiser and Alexis Bledel at the Screen Actors Guild Awards in Los Angeles.Chris Pizzello / AP file / Today

Their "Mad Men" characters had an ill-fated affair, but off-camera, Alexis Bledel and Vincent Kartheiser are excitedly celebrating their engagement, Bledel's rep confirms exclusively to Us Weekly. "They couldn't be happier," says a pal of the "Gilmore Girls" alum, 31, and Kartheiser, 33.

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Last June, Us broke news that the twosome -- Bledel played the mentally imbalanced mistress to his character, ad exec Pete Campbell -- had been "dating for a few months."

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Says another friend: "Vincent proposed a few weeks ago. She's been wearing her ring. It's huge!" In the past, Kartheiser has been linked to actress Rachael Leigh Cook; Bledel dated her "Gilmore Girls" co-star (and on-screen love interest) Milo Ventimiglia for more than three years.

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"They are so cute together!" another source tells Us of the spouses-to-be. It will be the first marriage for both, who attended the October nuptials of Bledel's "Sisterhood of the Traveling Pants" co-star Amber Tamblyn and David Cross.

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