NICK LACHEY about to be experience the joys of first time fatherhood.

The  former boy bander — who’s married to Vanessa Lachey (formerly Minnillo) — announced on Live! With Kelly that the couple is expecting their first child, due late summer or early fall.

Lachey  —  who was filling in as a  special guest co-host on Live!  — said that after Vanessa appeared on the show in early January, "she started to feel a little different, not herself. So she went to the store, got a pregnancy test, and it came back positive. So we are  having a baby!"

  "I've had a chance to do a lot of great things in my career and my life, but this is the one thing that, more than any other, I look forward to. The fact that it's actually here, it's overwhelming."

Lachey doesn’t know if it’s a boy or a girl, but he can’t wait to find out.

"We definitely want to know," Lachey added.

 "I can't take the knowledge that someone out there knows, but I don't know. It's like watching a sports game on TiVo."

Nick, 38, and Vanessa, 31, tied the knot in July, 2011.

Lachey’s ex-wife Jessica Simpson is also pregnant with her first child with fiancee Eric Johnson.  She’s expected to pop any minute, reported.