"I was overjoyed," says Kevin, 25. "It's been the most exciting thing in my life so far."
He added, "I'm excited and I'm nervous."
And the two confirmed it all to followers. Hetweeted: "Happy 2 be sharing this news!" She echoed the sentiment on her Twitter feed, too.
Brother Nick also tweeted a thumbs-up, saying, "Can't wait to welcome the newest addition of the Jonas family. Congratulations to my bro @kevinjonas & @daniellejonas."
Kevin married Danielle in December 2009. More details are promised to come on tonight's E! News.