"An estimated 684,500 state and federal prisoners were parents of at least one minor child in 2016 (figure 1, table 1). About 626,800 (47%) males and 57,700 (58%) females in state or federal prison were parents with minor children. Prisoners reported having an estimated 1,473,700 minor children."
Laura M. Maruschak, Jennifer Bronson, PhD, and Mariel Alper, PhD. Parents in Prison and Their Minor Children: Survey of Prison Inmates, 2016. Bureau of Justice Statistics, US Dept. of Justice. NCJ 252645. March 30, 2021.