Game of Thrones costars Kit Harington and Rose Leslie are engaged! 

It was the on-screen romance that sparked a thousand memes — and now, five years later, a real-life engagement.

Kit Harington and Rose Leslie are engaged, a source confirms to PEOPLE.

The actors first stirred up relationship rumors in 2012, in sync with their fictional 

Though they reportedly split after a year, they later reconciled and continued to fuel romance speculation until they officially confirmed the relationship in April 2016, making their red carpet debut as a couple at the Olivier Awards in London.

A month after going public with the relationship, Harington, 30, opened up about the early days of the romance, which began on set while shooting in Iceland for season 2 — sweetly admitting that those weeks were his favorite of the series, and for good reason.

“Because the country is beautiful, because the Northern Lights are magical, and because it was there that I fell in love,” he said in a cover story for 

. “If you’re already attracted to someone, and then they play your love interest in the show, it becomes very easy to fall in love.”

Back in 2014, Leslie, 30, also touched on her relationship with her heartthrob costar — and their famous season 3 sex scene — in an interview with PEOPLE.

“Kit is a lovely and funny man, and a dear friend,” she said. “We had known each other before we started working together on 

. It was always such a privilege to be working opposite him and such a blessing that we get on in real life because it made our characters more believable.”

“It was my first sex scene that I’ve ever done and it was weird,” she admitted. “But I felt that it was important for the characters and the audience to get to see just how much they have fallen in love. We got to see them in their own little world, with no outside interests or power plays or nasty surprises. It was just two characters finally getting together.”

Harington revealed he and Leslie have moved in together during a June appearance on 

The Late Late Show with James Corden

“I’ve moved in with my other best friend, Rose,” he said. “I’m very, very happy and it’s going well. She has all sorts of ideas for the house.”

“I said to her — because she moved into my house — I said, ‘Look, darling, it’s important that this is our space, that it feels like our space and that you haven’t just moved into mine. Move anything you want around — change anything or chuck anything out.’ ”

“So I went to the shops and I came back and said, ‘What did you decide?’ ” he continued. “And she went, ‘We’re moving the kitchen downstairs.’ ”

Nicole Kidman, who was also a guest on the show, then jumped in and casually asked, “Are you going to get married?”

“Oh, wow!” said Harington as Corden roared with laughter.

“No, I just think it’s kind of nice — if you’re going to live together, maybe to at least get engaged,” Kidman continued. “I’m working hard for her here!”

“I’ve been put on the spot by Nicole Kidman!” said Harington with a laugh. “I mean, it’s step by step, step by step.”

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