The Black Swan star, 52, and the French model, 21, announced on Tuesday that they are expecting their first child together.
Cassel shared the exciting news in an Instagram video featuring the happy couple — who have been married since August — on a beach in Bahia, Brazil.
In the short clip, the actor holds and kisses his wife’s growing baby bump, while Kunakey glows in her yellow bikini and oversized straw hat.
“Bonne année Feliz ano novo Happy new year #tellementdechance #danslavieriennestdû #lifeismagicneverforget #goooooooaaaaaaal,” he captioned the sweet video, which translates to “Happy New Year” in French and Portuguese.
Meanwhile, Kunakey shared a lone photo of herself smiling on the beach. In the sexy Instagram shot, the model poses naked with the straw hat covering her chest, while she shows off her pregnant belly.
“HAPPIEST NEW YEAR EVER #andifyoudontknownowyouknow,” she wrote alongside the scenic side-profile shot.
The exciting baby news comes four months after the pair tied the knot over the summer in an intimate ceremony in France.
The couple looked overjoyed as they were photographed arriving at the city hall in Bidart, France, nearly 500 miles from Paris. The Ocean’s Twelve actor looked mesmerized by Kunakey as he greeted her outside the venue.
The bride wore a custom Vera Wang strapless white gown with a plunging neckline and a princess skirt, while the groom wore a cream suit, pink dress shirt and dark sunglasses.
The newly married couple showed off their big smiles as they left the building, and shared a kiss outside.
Cassel and Kunakey have been together since 2016, when they met in Biarritz, France. The model first hinted at an engagement in May when she shared an Instagram photo of the two at a red carpet with a telltale engagement ring emoji.
Want all the latest pregnancy and birth announcements, plus celebrity mom blogs? Click here to get those and more in the PEOPLE Parents newsletter.
In August, Cassel and Kunakey were featured on the cover of Vanity Fair Italy in which the actor admitted he never thought he’d remarry again.
“I thought: I was married, I have two little girls, I did what I had to do; so I will be single,” he said. “It was fun but after a while I realized that my life was empty. I did not expect to meet someone, but it happened. And this woman is much younger than I would have imagined.”
In addition, the actor expressed his desire to be a father again, saying, “Children are the most wonderful thing that exists. It is through children, my daughters and beyond that I have learned more things.”
“They help me understand myself,” he added.
In an interview with The New York Times in August, the actor said he was confident that babies were in the couple’s future. “I’m 52 and I’m getting married with a 21-year-old girl,” he said. “I’m very much in love and sure we are going to make babies.”