The 29-year-old and his wife Una, who is a member of five-piece girl band The Saturdays, are already parents to two-year-old daughter Aoife Belle.
Una confirmed the news on her Instagram page with an image of her daughter wearing a T-shirt that read, 'I'm going to be a big sister'.
Una wrote: "I know lots of people have been guessing and Ben and I can now confirm that Aoife is going to have a baby brother or sister next year!!! We're all very happy."
The couple married in June 2012.