Internationally, incarcerated fathers and their children are often administratively invisible. The protective father–child relationship (FCR) is understudied. A secondary analysis was conducted to identify the number of all Dutch incarcerated legal fathers and their children; and several demographics and detention factors (e.g., prison length, offense type) were uncovered. Over 34% of incarcerated men were legal fathers, with approximately 12,000 children, mostly minors (64%), in each yearly count. Fathers differed from nonfathers by age, ethnic background, type of offense, and prison length. Follow-up research is needed to understand the interrelatedness of different demographics and detention factors and their impact on the FCR.