David Nail Hopes to Have a Fourth Child with Wife Catherine: 'We Would Like One More'

It's Tuesday afternoon, and David Nail is home alone with his 5-year-old daughter Lillian. Nail's wife Catherine has just left on an out-of-town trip with Lillian's twin brother, Lawson, and 22-month-old daughter Ellie, which means that the country music hitmaker will spend the next 60 hours trying his best to keep his darling daughter busy.

And yes, they have already gone on a Target run.

"I tried to get her to stay in the dollar bin this time," laughs Nail, 43, during an interview with PEOPLE. "But she had her mind set on some squishy thing that was nine bucks."

Of course, Nail made the purchase to make his daughter happy and put his own mind at ease, if only for a little while.

"She fell asleep right as we pulled into the neighborhood," Nail says of the return from their shopping excursion. "But of course, when I tried to get her to lay down in the house, she fought me." He laughs. "She was convinced that she wasn't tired!"

It's just another sweet and oh-so-relatable piece of the life of the Grammy-nominated singer/songwriter who has climbed the charts through the years with songs such as "Red Light" and "Nights on Fire," but now also finds himself living in a household with three children under the age of 6.

"I think both Lillian and Ellie are going to be just like Catherine," Nails says of his wife of 13 years. "But my son Lawson, he's very much like me. He's very sensitive and he's very shy. But he's got a really good ear and he's got a really pretty voice for an almost 6-year-old. He just doesn't really know quite yet if it's cool to sing, even though his father does."

Indeed, with the release of his latest song "Sunset Carousel" and the recent announcement that he will be back on tour this fall with his "Story to Tell Tour" featuring special guest Tyler Braden, Nail has found a way to combat his own self-proclaimed shyness while living within the country music spotlight.

And his kids have certainly helped him with that.

Granted, the couple did face their challenges when it came to starting a family, with both being very open about their struggles to conceive.

"All of our kids are here via IVF," Nail explains of going through in-vitro fertilization for Catherine to become pregnant. "We had tried IVF in between the baby and the twins and it wasn't successful. And it's weird because, obviously, it's a God thing. You can try to plan it, but obviously you have really no control over if it will work or not. So yeah, we talk all the time about the one that wasn't successful. What would they have been like?"

Nail grows suddenly quiet.

"But then we think, what would we have done with babies so close in age?" the Missouri native asks aloud. "Now, with the twins being 5 years old, they really are a huge help with the baby."

And all the children are growing faster than ever.

"My son has developed a little crush on this girl across the street," says Nail. "My wife and I joke around and say that he's already got his first summer fling, and he's 5½. It's so cute, but he's got it bad."

It's these sweet moments that now have the couple considering having a fourth child.

"I always defer to my wife because she's the one that has to carry the baby, but yeah, I know we would like one more," Nail says. "Catherine is so very protective of these embryos and so close to them. We have a trip out to California for a week in September, and we're sort of thinking that maybe a month or so after that, we would go ahead and try for one more. We would love to have a summertime baby."

And this time, they hope it happens without a hitch.

"The twins were so difficult to have," Nail remembers. "We waited so long, and it was such an emotional thing that I think we both at first were just so grateful to even have two kids. You almost feel guilty wanting more."

And if Lawson has any say as to what sex that fourth child should be, he would love to finally have a brother.

"Lawson is very adamant about it," says Nail with a laugh. "He doesn't even allow himself to think about it being another girl!"