'It's impossible to keep a secret...especially one as wonderful as this,' reads a statement.
'We want to be the first to share this great news with everyone that we are expecting a new addition to our family.'
John, 56, and Kelly, 47, have not specified what the 'new addition' will be.
The couple are parents to Ella Bleu, 10.
In January 2009, their 16-year-old son Jett died after suffering a seizure while at the family holiday home in the Bahamas.
Where to next?
- How to boost your fertility
- Your pregnancy week-by-week
- Pregnant celebrities