In 2009, Kelley and Haywood penned a song called "It's Only" for Danny Gokey's debut album, My Best Days, with "I Run to You" cowriter, Tom Douglas. That same year, the two also wrote "Love Song" with Blake Shelton and Miranda Lambert, which Lambert would later record for her third studio album, Revolution, and Kelley would sing background on.
Kelley is married to music rep Cassie McConnell. The couple wed in a Nashville courthouse in late June 2009 as a legal formality before having a destination wedding in the Bahamas. After the wedding, Lady Antebellum tweeted a photo of Kelley showing off his wedding band, saying, "What is that you see on Charles' hand... yep a wedding ring!!!" McConnell represents several country musicians, including her brother-in-law, Josh Kelley. Charles and Cassie wed on July 6, 2009. On Aug 7, 2015, the couple announced that they were expecting their first child in February 2016. On August 28, 2015, his wife Cassie appeared on Good Morning America to reveal her fertility struggle and also announced they were expecting a baby boy. The couple welcomed their son Ward Charles Kelley on February 11, 2016.
Kelley had the lyrics, "All your life, you were only waiting for this moment to arise," from the Beatles song, "Blackbird", tattooed on his right forearm in early 2009. In 2010, Kelley got a second tattoo, a design of the "flower of life", on his upper left arm.