McGwire married Stephanie Slemer—a former pharmaceutical sales representative from the St. Louis area—in Las Vegas on April 20, 2002. On June 1, 2010, their triplet girls were born: Monet Rose, Marlo Rose, and Monroe Rose. They join brothers Max and Mason. Mason was drafted by the Chicago Cubs in the eighth round of the 2022 MLB draft. They reside in a gated community in Shady Canyon, Irvine, California. Together they created the Mark McGwire Foundation for Children to support agencies that help children who have been sexually and physically abused come to terms with a difficult childhood. Mark has a son, Matthew (b. 1987), from a previous marriage (1984–1990, divorced) to Kathleen Hughes.
McGwire married Stephanie Slemer—a former pharmaceutical sales representative from the St. Louis area—in Las Vegas on April 20, 2002. On June 1, 2010, their triplet girls were born: Monet Rose, Marlo Rose and Monroe Rose They join brothers Max and Mason. Mason was drafted by the Chicago Cubs in the eighth round of the 2022 MLB draft. They reside in a gated community in Shady Canyon, Irvine, California. Together they created the Mark McGwire Foundation for Children to support agencies that help children who have been sexually and physically abused come to terms with a difficult childhood. Mark has a son, Matthew (b. 1987), from a previous marriage (1984–1990 divorced) to Kathleen Hughes.