A new study of thousands of male sex offenders found that close relatives of people convicted of sexual offenses were up to five times more likely than average to commit similar offenses themselves.

Researchers found that about 2.5 percent of brothers and sons of convicted sex offenders are themselves convicted of sexual offenses, compared to about 0.5 percent of the wider public. The correlation, according to the study, is largely due to genetic factors rather than shared family environments.

“Importantly, this does not imply that sons or brothers of sex offenders inevitably become offenders too”, Niklas Langstrom, professor of Psychiatric Epidemiology at Sweden’s Karolinska Institutet and the study’s lead author, said in a statement. “But although sex crime convictions are relatively few overall, our study shows that the family risk increase is substantial. Preventive treatment for families at risk could possibly reduce the number of future victims.”

The study, which analyzed data on 21,566 men convicted of sex offenses in Sweden between 1973 and 2009, was published in the International Journal of Epidemiology.

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Write to Noah Rayman at noah.rayman@time.com.