Grier has a daughter from a previous relationship named Sherryl Brown-Tubbs. He later married Bernice Lewis, who had one child, Denise, whom he adopted before getting divorced. He then married Margie Grier and had a son, Roosevelt Kennedy Grier, in 1972. He and Margie divorced in 1978 and remarried in 1980. Margie Grier died on June 10, 2011. He married Wichita school Teacher Cydnee Seyler on April 30, 2013. A nephew, Mike "Big Daddy" Grier, followed his uncle's career in Sports when he enrolled as a student at Boston University, but he played ice hockey instead of football.