Michael Robert Henrion Posner was born on February 12, 1988, in Detroit, Michigan. He was raised in Southfield, Michigan, a northern suburb of Detroit. He has a sister who is six years older. His father was Jewish and his mother is Catholic. Posner went to Bingham Farms Elementary School, Berkshire Middle School and graduated from Groves High School, where he ran varsity track and cross-country. He attended Duke University, where he was a member of Sigma Nu fraternity. He graduated with a B.A. in Sociology with a 3.6 GPA.
Posner's father, Jon, a criminal defense lawyer, died on January 11, 2017; his mother is Roberta Henrion; and his sister, Emily Henrion Posner, is a civil rights attorney.
