ET can confirm that the 57-year-old actor's girlfriend, Anna Eberstein, is pregnant. The couple already has a 2-year-old daughter and a 5-year-old son named John Mungo. Grant also has a 4-year-old son, Felix, and a 6-year-old daughter, Tabitha, with Tinglan Hong.
On Sunday, Eberstein escorted the Paddington 2 star to the 75th Annual Golden Globe Awards and displayed a small baby bump in her all-black outfit.
The two were also spotted at the airport in New York City on Monday, where again the Swedish television producer's growing belly was evident in a fitted black top.
On Tuesday's Live With Kelly and Ryan, Grant opened up about fatherhood and quipped that his kids "hated" the Paddington sequel. "My own children loathed it," he said. "They loathe me. They said, 'Why are you in it so much?'"
Grant then joked that even though his children are "ridiculously young," they are still "very much" embarrassed by him.
ET reached out to Grant's reps regarding the baby news, but they could not be reached for comment.