"We've been best friends for the longest time and now we're just kind of taking the next step and it's been really fun. We're having a great time," Joe tells Ryan Seacrest on his KIIS FM radio show. "I guess we kind of figured that one day it would happen but we didn't feel like it was the right time."
Demi added, "Being best friends for a while, over time feelings grow, and for me, as much as I wanted to deny it, the feelings were always there."
Demi will join the Jonas Brothers for "Camp Rock: The Final Jam" July 13 on Disney.
Related stories: A Jonas Brother is Engaged!
- 16 hours ago See which books are being turned into movies in 2018