Joey McIntyre with his wife Barrett Photo by: Roger Karnbad / Celebrity Photo

There's going to be another new kid on the block: Joey McIntyre tells PEOPLE that his wife Barrett is expecting their second child – a boy – in December.

"I still can't get over it," says the singer, 36, who also has 20-month-old son Griffin. "We feel so blessed."

So far baby no. 2 has already managed to throw his parents for a loop. "My wife actually took the [pregnancy] test but she thought it was negative," says McIntyre. "She came out and gave me this look like, 'No.' Then she showed me the test and I said 'It's positive! What the hell?'"

Then when the proud parents, who were convinced they were having a girl, found out they were adding another boy to the brood. "We were shocked," says McIntyre, who had his daughter's name picked out. But they're hardly disappointed. "It's going to be a trip to have a couple of boys around."

Griffin is more than ready for his new brother, says McIntyre, who grew up the youngest of nine kids. Along with constantly kissing his mommy's belly, "We say to him all the time, 'Do you want us to bring home a baby?'" Griffin's response? "Please!"

The toddler has also inspired Daddy to start a book drive through the Let's Get This Foundation. While on the road, McIntyre and the rest of the New Kids have collected thousands of new children's books and distributed them to children in need in various cities.

"My wife is an avid reader and from the get-go she sat down with him and read with him. You see the importance of that," says McIntyre, who also reads to Griffin some of his favorites like Good Night, Gorilla. "Then I found out there's a lack of age-appropriate books for kids, I saw a huge void and I knew our fans could step up." McIntyre hopes to reach 25,000 children by the time the guys wrap up their tour on July 18.

But the big question remains: Will his family grow to include nine kids? "I think we have a deal to keep going until we have a girl," says McIntyre with a laugh. "That's what my wife says."