Insiders say Blake Shelton and Gwen Stefani are working hard to have a baby, and it is making their relationship stronger.

In the latest issue of Us Weekly, multiple sources revealed that the country crooner and the rock vocalist are very eager to expand their family. Stefani is already a mother of three boys — Kingston, 11, Zuma, 9, and Apollo, 3 — but Shelton has yet to have a baby of his own.

An insider close to Shelton said, "They will get married one day, but right now they are hyper-focused on getting pregnant."

At 48 years old, Stefani is said to be still very positive that it could happen, considering she conceived her youngest when she was 43. "They are incredibly hopeful," the insider added.

Sources said the nine-time Country Music Association Award winner was very upfront with his plans of having a family, and Stefani was willing to try from the start. The couple has reportedly been trying to conceive for at least a year now, but it's not working out the way they want it to.

Instead of this taking a toll on their relationship, however, reports said it is bringing them even closer together.

"Blake and Gwen's excitement over becoming parents has made their relationship rock solid," an insider told Hollywood Life.

The source added that Shelton, with his great sense of humor, often uses the baby topic to diffuse arguments with his partner. It also doesn't matter that they don't have a baby on the way yet; the couple, along with Stefani's boys, often talks about baby names.

"They love to play argue over baby names — Blake picks names like Billy Bob or Rusty, and she, of course, wants hip names like Stella and Emma," said the insider.

With three boys already, Stefani is said to be hoping for a girl this time around. The source said Shelton is on board, as long as it is a "healthy baby."

Shelton was previously married to fellow country singer Miranda Lambert. Reports speculated that the former couple ended their marriage in 2015 because Lambert refused to start a family. At that time, Stefani was already in the process of breaking up with her husband of 13 years, Gavin Rossdale.