(NEW YORK) -- The father-in-law of missing Utah mom Susan Powell said the two had a highly flirtatious relationship that was unknown to his son, who says that he had nothing to do with the 2009 disappearance of his "unstable" and "very sexual" wife.
Steven Powell, Susan Powell's father-in-law, alleged that his missing daughter-in-law would frequently make passes at him and that he had a relationship with her that was "a little beyond the pale."
"There was really a disconnect between the Susan who was a faithful, loving wife, and the Susan who was a very flirtatious, sexual being," Steven Powell told ABC News' Good Morning America. "Father-in-law, daughter-in-law flirting with each other, maybe some sexual touching or whatever. And -- I enjoyed it, frankly. Susan was a joy to be around in so many ways, not just those ways."
The only named person of interest in the case of his missing wife, Josh Powell, 34, has maintained that his wife left on her own when she disappeared Dec. 6, 2009 from their West Valley City, Utah home.
"Everyone who knows me knows that I would never hurt her and I would never hurt my boys," Powell said in an interview with ABC News. "I would never hurt anyone."
Susan Powell, then 28, was last seen on Dec. 6, 2009 at the home she shared with her husband and their two young sons Charlie, then 4, and Braden, then 2.
Josh Powell told authorities that he had been camping with the couple's boys -- in the midst of a blizzard -- the night his wife vanished. He has taken his kids to live with his father in Washington State since the disappearance.
Powell described his missing wife as an erratic and depressive person who contemplated suicide at several points in her life and would leave the house barely dressed.
Powell told ABC News that he feels that his wife may still be alive. Though he said that he is unaware of any time that his wife was unfaithful to him, he wonders if she left him and their two young children for another man.
"She's a very sexual person," he said.
Josh Powell's characterization of his wife was supported by his father Steven Powell, who told ABC News that his son was unaware of the relationship he says he had with his daughter-in-law. He also said that the two were in love.
"Josh wasn't aware of a lot of these things at first because the first two or three years of his marriage -- it was really pretty much not something that really came to light," Steven Powell said. "We interacted in a lot of sexual ways because Susan enjoys doing that."
Steven Powell plans to post his daughter-in-law's teenage journals on the website SusanPowell.org. According to the Salt Lake Tribune, he says that the journals show that his daughter-in-law is capable of walking out on her husband and their two sons.
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