The Fun frontman thinks it would be ''fun'' to have a baby with his 'Girls' actress girlfriend - who he has been dating since 2012 - but suggested his partner isn't ready just yet.
Jack said: ''I think about it a lot and it seems like fun.
''We talk about it all the time... But Lena has her own thoughts on that.''
The 32-year-old musician believes the key to their relationship is ''trust'' and giving one another the space they need to work.
He said: ''There's a lot of trust there.
''When it comes to people's art, you need to give them the space they need.
''When you start considering other people and their feelings, you can really f**k up what you are doing.''
Despite his hectic schedule, Jack - whose sister died aged just 13 from brain cancer - needs to follow a specific routine because he suffers from anxiety and obsessive compulsive disorder (OCD) and the conditions also influence his writing.
He told Grazia magazine: ''On tour, even if I feel fully unravelled as a human being can, there's still a schedule I have to follow. I can't become dysfunctional because I have to be where I have to be.
''We all have moments in our lives that change things forever. I write a lot about how I lost my sister. I struggle with anxiety and depression a lot. It's ongoing - everything goes through that filter.''
It's been five years since Purity Ring released Another Eternity, but little has changed in their overall sound and macabre lyrical themes now that...
We need music now more than ever.
Mystery Jets, Purity Ring and more coming soon...
Just over two years since the release of her vibrant debut album, Anna Burch is back with her second full-length album: 'If You're Dreaming'.
What have we been listening to on repeat?
The Chats' debut album High Risk Behaviour is the most punk thing we've heard in years.
Nature-inspired songs we just can't get enough of.
What do you need to know about buying headphones?