"It's true – Danielle is pregnant! Can't even imagine how excited we are," the musician and reality star, 25, Tweeted Tuesday. "I can't wait to share this with my best friend. I love you baby."
The couple, who married in December 2009, told PEOPLE last July that babies were beginning to be on their minds.
"Having kids is a big question right now; it does come up a lot," Danielle, 26, said at the time.
"We're at that [3-year] mark and people are like, 'All right guys, what's your plan? When are you going to have those grandkids?'" adds Kevin. "I'm starting to feel that pressure a little bit."