The two stars are already parents to a 2-year-old son.
Kit Harington and Rose Leslie are preparing to welcome baby no. 2! The 36-year-old Game of Thrones star shared the news on The Tonight Show, revealing that their 2-year-old son, whose name they have not revealed, is preparing to have a sibling.
"He's really good. He's about to get the shock of his life, which is he's about to get a brother or sister," Harrington announced as host Fallon looked shocked and shook his hand.
The British actor admitted to being "terrified" this time around as he prepares to welcome another child.
"With the first baby, you're walking on clouds and dancing through fields of daises for nine months. Well, the man is, anyway," Harington quipped. "This time the reality check is much shorter. You get practical real quick."
As for Harington and Leslie's firstborn, he hasn't quite grasped the concept of welcoming a sibling.
"I'm not sure he's quite conceptually understood it just yet. We're trying to get him ready for it," Harington explained. "We point to Rose's tummy and we say, 'Mommy's baby, Mommy's baby.' And he points at his tummy and goes, 'My baby.'"
Despite the little guy's confusion, Harington noted that he and Leslie think their son "might be quite smart."
"Well, it's surprising seeing as we're both actors," Harington quipped. "We're not sure quite where that's come from... He loves applause. Every time he does something good, we give him applause, and we're worrying that's kind of pushing him towards acting. We're a bit like, 'Eh, you might be too smart for this. You know, go save the world. We're thick. We had no choice.'"