Charton shared the news by posting a sonogram on Instagram writing, "My favourite surprise so far"
Kieran Culkin is going to be a dad!
“My favourite surprise so far,” the former model captioned a sonogram. “We had no idea how much we wanted this until it happened.”
“We’re excited/terrified/ecstatic/unprepared but we cannot wait to meet our little unexpected creation in September,” Charton added.
The baby’s sex has not yet been revealed.
A rep for Culkin, 36, did not immediately respond to PEOPLE’s request for comment.
The sweet news comes just a year after Culkin revealed the couple had no plans to expand their family.
“It just seems like a lot to take on,” the Succession star told The i.
“I suppose if she gets pregnant, that would be fine but it’s really not on our horizon,” Culkin explained to the outlet.
“Not one of us have started our own family,” said to The i of his siblings Macaulay Culkin, Rory Culkin, Quinn Culkin, Christian Culkin, Shane Culkin and Jennifer Adamson. Culkin’s sister Dakota died at the age of 29 in 2008.
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“My mother is one of 11 kids and had seven kids and she has no grandchildren, so think about that?”
Charton and Culkin have been married since 2013.
Culkin met “this most beautiful girl” at a New York bar, the actor told The i. She happened to be there with another man.
“I asked if he was her boyfriend and when she said no, I asked if I could be her boyfriend. We’ve been together ever since,” Culkin told the outlet.
“When someone is as beautiful as my wife, you just want to be close to that.”
Culkin previously dated Emma Stone.
Charton frequently shares photos of the adorable cats on social media.