"We're excited to have another little member of the family coming in," says Bryan.
Bryan, 33, says having son Bo, who turns 2 in March, helped ease their nerves about parenting. "When you successfully brought one in the world, you are a little more confident in your ability to do it the second time," he says. "We're a little more relaxed – you know everything that can come at you."
The singer, who recently scored his first No. 1 country hit with "Do I," says that he and Caroline, 30, have already begun to prepare Bo for the arrival of his little brother or sister.
"When he wants to play around and jump on Caroline we're like, 'You have to be careful. Mama has a baby.' And he'll put his finger on her belly and point and say, 'Baby,' " says Bryan.
As for the new baby's gender, Bryan says he and his wife plan to find out before the birth. "I'd lose too much sleep wondering otherwise!"