According to Vulture, Kartheiser lives in Los Angeles but has been staying in Brooklyn with Bledel, whom he met two years ago when she guest-starred as his character Pete's mistress on Mad Men's fifth season.
Although they met on the set, the thesp said they didn't date until after season five wrapped.
"We were completely professional," Kartheiser said. "We never saw each other out. We never—it was nothing, it was just work."
Meanwhile, several of his costars including Jon Hamm, and Mad Men creator Matthew Weiner were rooting for them.
"I did know he liked her from a very early point," Hamm said. "I was a supporter of that union." Weiner also commented on the couple, adding, "I told Vinnie that they would be great together. I was like, ‘Don't blow it!'"
He also told the show's writers that the two would get married. "Honestly, they're a really good match," Weiner continued. "They're both very down to earth, with a sense of responsibility and strong family ties. And they've been acting since before they can remember, which makes for a very special personality. It's not just that I thought they would look cute together."
But, he said, with a laugh, "Even with all of Alexis's amazing qualities, I think that if she had not been such a good actress, he would not have been interested."
The couple got engaged in March 2013 after dating for a few months.