Steven Powell is due to be released next month from the Washington prison where he's been serving 30 months for voyeurism.
Department of Corrections spokeswoman Norah West says Powell will be released at the end of his sentence March 23.
Powell is the father-in-law of Utah mother Susan Cox-Powell, who disappeared in 2009. His son, Josh Powell, was a suspect before he killed himself and his two children in an explosive house fire in 2012.
Steven Powell was convicted of voyeurism for taking photographs of two young neighbor girls as they used the bathroom in their home. A judge has ordered the Pierce County Sheriff's Office to sell his home near Tacoma to help pay the $1.8 million Powell owes his victims, but the Deseret News in Utah reports (http://is.gd/UVYXPu ) that has been put on hold while Powell fights the sale.