John, 54, confirmed the happy news that his fiancée Caitlin McHugh, 31, is pregnant to PEOPLE magazine as part of a cover interview with the title.
John pictured with Caitlin in October 2017
'I always wanted to be a dad. Clearly I had to do some work on myself, first,' he told the mag.
'I have a youthful thing. People say, "Oh, you look young. You'll start believing you're gonna live to be 150." And then you wake up and go, "No, man, this is it. This is not a rehearsal."'
The announcement is a joyful addition to an already exciting year for the couple, who got engaged back in October, after John popped the question during a trip to Disneyland.
'I asked...she said yes! ...And we lived happily ever after💍' John wrote on social media at the time, alongside a custom illustration of the couple in front of the iconic theme park castle.
Caitlin, meanwhile, posted a photograph to her Instagram account to mark the sweet moment, saying: 'I kissed the boy and said...yes! That's what you do when the sweetest, most romantic Prince Charming treats you like a princess and asks you to be his 💍'
'We have the same morals and the same values, that all clicked nicely. So we said, "Oh, well, maybe we should have a family,"' John explained to PEOPLE.
Although they have shared the milestones with fans, Caitlin added that they hoped to live their life on a fairly private basis.
'We like to keep our lives private because we've seen what relationships in the public eye can be like and we just like our privacy,' she said.
'We don't want the commentary from the masses about what our relationship is or should be. We're very happy together and we hope to be so for a long time.'