Storm, 35, announced the happy news with a teasing picture on her Instagram account inviting readers to find out why she hadn't chosen mulled wine on a trip to a Christmas market. She then followed up with an official statement on her blog.
In a twist of fate, it turns out that Storm discovered her pregnancy on the anniversary of both the day she and Ronan became friends, and their wedding anniversary.
https://www.instagram.com/p/BNrOpp5B6qR/?taken-by=stormykeating&hl=en'On the 17th August in 2010, my husband and I became friends. On the same day five years later we became husband and wife,' she wrote.
'We're now very excited to announce that a year later (and again to the exact date) we became parents-to-be!! And so THAT'S why I passed on the mulled wine.'
'Words cannot describe how overwhelmed with happiness we are. We feel so blessed to be adding another little Keating to the family and this news is like all of our Christmas wishes coming true.'
'This Christmas we'll just be asking Santa to keep our baby safe and to spread some extra happiness and joy to you and all your families also.'
Ronan followed up with an image on his own Instagram of one of his array of tattoos, writing: 'Glad I saved this prime real estate #Luckiestmanintheworld #anotherlittlekeating'
Ronan has three children - Jack, 17, Missy, 15, and Ali, 10 - from his previous marriage to ex-wife Yvonne, from whom he split in 2012, but the new arrival will be the first child for Storm.
At the end of the blog, she added: 'I already have so much blog content to share to other mothers and mothers-to-be... Hilarious stories, the reality of pregnancy and navigating through the endless range of nasty products to avoid when you have a little bub in your tummy etc. So much to share!!'
In a previous interview with HELLO! magazine, Ronan said that Storm's presence had made his relationship with his children easier, because they 'can see how happy I am. And it's about making them know they are loved.'
After reading the responses to her pregnancy news, Storm tweeted: 'Humbled by all the beautiful msgs today, wish I could respond 2 them all! Thanku so much -the kindness makes this time even more special ❤️👶'