Zac and his wife make room for baby!

"I am utterly thrilled at the thought of becoming a father," ZAC HANSON tells People.com.

His wife, KATE, adds, "I can't wait to meet this person. This is the most amazing time for us. It's the most romantic thing we've ever done."

Zac, 22, is currently on tour with older brothers TAYLOR and ISAAC, both of whom have young children of their own.

"It will be really fun to see [them] grow up together," says Zac. "I know watching them is going to inspire a lot of music."