A source told Belfast Live: 'Jamie and Amelia have another baby on the way.'
The couple – who married in 2013 - also share two daughters, Dulcie, who was born in 2013 and Elva, believed to have been born in 2016.
During an appearance on British TV show This Morning in 2016, the Irish actor admitted he would love to devote more time to his family.
'It's brilliant, it's the most magical thing in the world. I love it,’ he gushed about fatherhood.
'I want to be busy but I'm also aware I'm a young father and I want to spend time with my kids.
'So they come everywhere with me, which we can afford to do at the moment before they start school.'