Along with his siblings, David was homeschooled growing up. He and his siblings were raised as active participants of Bill Gothard's Institute in Basic Life Principles, and regularly attended the yearly Advanced Training Institute conferences in Big Sandy, Texas.
His parents were strict growing up, and he and his siblings had weekly scheduled fifteen minute meetings of one-on-one time with their parents.
In 1996, his father made the decision to quit his job and begin working in full-time ministry at a local juvenile detention center. David often accompanied his father on these trips and led Bible studies for incarcerated young women.
On June 23, 2021, it was announced that David was in a courtship with Hannah Reber. David said: "Hey everyone, I'd like you to meet Hannah Reber! I have really enjoyed getting to know her. God gives good gifts." Hannah said: "God gives good gifts. I've enjoyed knowing you. Can't wait to start this adventure with you." They met when David visited Arkansas to help his sister Anna after his brother-in-law Joshua Duggar was arrested and released on bail and confined to house arrest at Hannah's family's house. On June 27, 2021, Michael Keller mentioned in a sermon at his son-in-law David Waller's church that his son David was courting a "godly young lady".
On July 15, 2021, David proposed to Hannah Reber. Of their engagement, Hannah said:
"Nothing about David or I was prearranged. We chose each other. And I’d choose him again. He is giving and loving and kind. He’s helped me to see my value and see how beautiful life is. I haven’t always felt valued or seen. It’s overwhelming. It feels a lot like God’s love."
On November 19, 2021, David married Hannah Marie Reber at Amy's Wedding Barn in Fayetteville, Arkansas. David's best man was his brother Nathan. His groomsmen were his brother Daniel, his brother-in-law David, his family friends Jedidiah Duggar, Nathan Paine, and Matthew Waller, and three unknown friends. His junior groomsmen were his nephew Michael and an unknown boy. The ring bearers were David's nephews Paul and Mason. Hannah's maid of honor is unknown. Her bridesmaids were her sister-in-law Hannah Reber, David's sister Susanna, David's family friends Josie Duggar, Lauren Duggar, Katelyn Duggar, Lauren Nakatsu, and Lily Swanson, and three unknown friends. The flower girls were David's nieces Mackynzie, Noelle, Meredith, and Maryella.
On June 20, 2022, David and Hannah announced that they are expecting their first child, a girl, due November 2022.
David and his brother Nathan currently own and operate Keller Brothers Lawn Care in Palatka, Florida.