In a new interview, the Only Fools and Horses star shared his surprise after learning that a brief relationship he had with actor Jennifer Hill in 1970 resulted in the birth of Abi Harris.
Following the revelation, Jason, 82, is said to be building a relationship with Harris – who is also an actor – along with her 10-year-old son Charlie.
Speaking to The Mirror, Jason said that “to say it was a surprise to find out I had a daughter from years ago is an understatement”.
“However, on settling with the news, I am delighted that I am now able to get to know Abi and so we meet up when we can,” he added.
“My wife, Gill, and daughter, Sophie, have been very supportive and understanding and have embraced Abi and welcomed her and her young son into her now wider family.”
In 2005, Jason married his wife Gill Hinchcliffe after they met on a TV set. The pair share 22-year-old daughter Sophie.
According to reports, Charlie spent time with his grandfather at his Buckinghamshire home over Christmas.
Jason continued: “We hope we are all allowed the privacy to continue our new relationship and get to know each other more and more.”
Jason rose to fame playing Derek “Del Boy” Trotter on Only Fools and Horses between 1981 and 1991, reviving the character in multiple specials until 2003 and a Sport Relief sketch in 2014.
Last year, the actor backed calls for the sitcom to be rebooted.
“I’ve always loved Del Boy, who is such a wonderful loser,” he said. “I would love to revisit him; I need someone to write me a script.”
After Only Fools and Horses went off the air in 1991, there have been multiple attempts to revive the series in various forms. These included spin-off The Green Green Grass and prequel Rock and Chips.