"Willa Gray, you continue to amaze me with your heart, your kindness, your selflessness, and your hilariousness," Thomas Rhett said

Happy Birthday, Willa Gray!

On Sunday, Thomas Rhett shared a sweet tribute post to his birthday girl, who celebrated her fifth birthday. "Ok I’m really sorry for all the posts today but we went straight from Halloween to Willa Grays’s 5th birthday," he began his post. "WG you continue to amaze me with your heart, your kindness, your selflessness, and your hilariousness."

"You make me such a better human being, and I’m inspired by you every single day. You may be 5 but you already act like your [sic] 15. You are the MOST amazing big sister that AJ and Lennon could ask for," the country singer continued. "I can’t wait to watch you grow and be there with you every step of the way. To my beautiful baby girl, happy birthday sweet pea!"

The proud dad then shared several photos of his daughter, including a photo of them together when she was just a baby.

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The "Marry Me" singer shares daughter Willa Gray with wife Lauren Akins. The couple, who recently celebrated their 8-year wedding anniversary, adopted their first daughter from Uganda in 2017.

In April 2016, Willa — known then by her nickname “Blessing” — was just one of many orphans in a children’s home Akins visited while working in Uganda with the Christian charity 147 Million Orphans. At the time, the couple had been trying to get pregnant with no luck, and had just begun to consider adoption. "She really does live up to her nickname in Uganda: She is just the biggest little Blessing that ever has walked the earth," Akins previously told PEOPLE of the toddler, who'd been brought to the children's home soon after her birth in November 2015.

Rhett and Akins went on to welcome two daughters, 3-year-old Ada James and 8-month-old Lennon Love.

On Saturday, Rhett and Akins dressed up their adorable trio for Halloween and shared some sweet snapshots of their costumes.

Akins captioned her post with a famous quote from Winifred Sanderson in Hocus Pocus. "'Sisters, All Hallow's Eve has become a night of frolic, where children wear costumes and run amok' 🎃👻🖤," she said.

"Hope everyone had a fun Halloween! The last pic of Ada James is kinda creepy," Rhett wrote alongside his post, which featured a photo of Ada James surrounded in fog and overlooking a graveyard.