'It wasn't planned,' 25-year-old Jack admits, but says he is 'just really happy about the whole thing. It's going to be a new chapter in my life!'
Jack says his parents - hellraiser Ozzy Osbourne, 62, and mum Sharon, 59 - are also 'very, very excited' by the prospect of a new addition to the family (suggesting there's a whole lot of excitement going down in the Osbourne house right now!).
In fact, Sharon - in her excitement - has already gone on the record to say just what she expects her new grandchild to call her - and it most definitely isn't granny!)
Despite obviously being totally chuffed (or perhaps that should be 'excited!') at the prospect of being a dad, Jack says he needs to respect his fiancée's privacy and will not be going into much detail about their forthcoming arrival.
He told Star magazine: 'You can ask me any question you want, but I want to respect the privacy of my fiancée and she's not here to answer your questions about her and her child. I do understand you're trying to fill your pages with the excitement of my news, but I'm not going to go into much detail. No more than what you can read on Twitter.'
Blimey! We never had him down as such a gentleman! Such an EXCITED gentleman!
Read the full story in this week's Star magazine - out today