Thousands of young people are sent to prison every day, leaving behind scores of brothers and sisters researchers know very little about.

Over 5 million kids in the United States currently have or have had a parent in prison. That works out to about one in 14 American children—a majority of whom are under age 10. Broken down by state, children with incarcerated parents can represent 3 to 13 percent of the population, according to “A Shared Sentence,” a report by the Annie E. Casey Foundation. The unusually intense stress that these children face has been well documented and studied. That’s mostly due to researchers’ emphasis on the parent-child relationship when analyzing incarcerated populations—and how little support is available for those left-behind children who are forced to stand by as their primary role models, caregivers, and providers are put behind bars.

But incarceration also affects a separate number of children who have been isolated from another profound relationship: They are the children with siblings in jail or prison—and much less is known about them. It isn’t even clear how many of them there are.

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