How Kimberly Schlapman's Infertility Issues and Daughter's Prayers for Sibling Inspired Kids' Book

Kimberly Schlapman and her bandmates of Little Big Town were made famous by their songs of love and heartache. In an exclusive interview with PEOPLE, Schlapman reveals just how familiar she is with both emotions.

The singer’s debut children’s book A Dolly For Christmas — a story about how Schlapman’s elder daughter so wanted a sibling that she wrote a letter to Santa — is a story of hope and faith that stemmed from Schlapman’s years-long struggle to conceive naturally and, later, the challenge of adoption. Schlapman, 50, shares 12-year-old daughter Daisy Pearl with husband Stephen Schlapman. In January 2017, they announced they’d adopted a baby girl, Dolly Grace.

A Dolly For Christmas, which will be released on Oct. 6, reveals just how big a part Daisy played in the expansion of their family. (PEOPLE has a first look at the cover.)

“[Daisy] never stopped believing and where, at times, my husband and I were discouraged and heartbroken over things not working out, Daisy never gave up,” Schlapman tells PEOPLE. “One day, her prayers and her dreams were answered in the most incredible way. She now has a baby sister that she loves more than life.”

Schlapman worked with her elder daughter to create the book (Daisy wrote the forward). They’re both excited about inspiring children and parents with their story.

“I just want people to be hopeful and to know that if they’re in the middle of a struggle, they are not alone,” the country star says. “We walked those same roads, and they are very, very difficult. But, in the end, there is restoration and there are children who are waiting for them.”

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The artist’s journey towards motherhood first began when she was married to her first husband, Steven Roads. They were unable to conceive naturally and in 2005, Roads died unexpectedly of a heart attack.

It was only after Schlapman returned home from her honeymoon with her new husband, Stephen, whom she married in 2006, that she learned she was pregnant with her miracle baby, Daisy Pearl.

“My Steve and I, we didn’t even think we could get pregnant, so of course we talked a lot about adoption,” Schlapman remembers. “But on our honeymoon, we brought home a little souvenir, a huge surprise, and that was Daisy. She was a miracle.”

By the time Daisy was 4 years old, she was begging for a sibling, her mom explains.

“One time she said to me, ‘Mommy, if I don’t ever have a brother or sister, then my children will never have aunts or uncles or cousins,’ ” Schlapman says. “She so badly wanted a sibling.”

Despite their prayers as a family, the Schlapmans struggled to conceive naturally. In an even more devastating turn, their fertility treatments also failed.

“We did artificial insemination, and that didn’t work, and then we did two full rounds of in vitro fertilization,” Schlapman says. “And those both ended in loss, so it was just a lot of heartache on the road to trying to have a baby.”

Eventually, Schlapman and her husband decided to adopt a baby — they weren’t particular about the baby’s sex or race. After filling out reams of paperwork, they were finally approved for adoption in the beginning of December 2016, but were told they might have to wait up to two years before getting a child.

“[Daisy] was still praying every day. She was really excited now that we were in the adoption process and just had her little heart energized again for the possibility of a sibling,” Schlapman says. “Because her prayers weren’t answered how she wanted at the moment, she decided to take matters into her own hands. She wrote a letter to Santa Claus.”

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A week after Daisy sent the letter, the family attended a Christmas party at the adoption agency.

“[Daisy] sat in Santa’s lap, and she said, ‘All I really want for Christmas is a baby brother or sister,’ ” the singer remembers. “Santa Claus said, ‘Wow, I’m not sure even I could do that.’ I’ll never forget her little face, her innocent little eyes looked at him. She said, ‘Yeah, but I know you know God, and I was thinking maybe you could talk to him.’ ”

Despite the adults’ doubts, Daisy’s wish came true. A few days later, the Schlapmans got a call about a little girl who needed a home. Dolly Grace was with them just a few days later, right before Christmas.

“She is our absolute Christmas miracle,” Schlapman says of the newest addition to the family. “I think that faith is what got us through all the disappointments — and our love, our huge family bond and the love we have for each other.”

Daisy’s letter to Santa is the inspiration behind A Dolly For Christmas. Schlapman hopes the story will inspire other families to maintain their faith, especially when facing infertility issues. The book is also a tribute to her daughters’ love for each other. One night, Schlapman remembers coming home and the girls had fallen asleep in bed together.

“I went in there, and I was moving everybody, and Daisy looked at me,” Schlapman says. “Dolly had fallen asleep in her arms, and [Daisy] said, ‘Mommy, I don’t know what this feeling is, but it’s the best feeling I’ve ever had in my whole life.’ ”

The next day, Daisy explained what she meant to her mom: “Mommy, I think Dolly is my first love.”

A Dolly For Christmas will be published on Oct. 6 by Little, Brown Books for Young Readers.