The woman, a resident of the district's Khajuwala area, has alleged that her father-in-law, Deeparam, had first raped her two years back when her husband was out of station.
"He had been raping the woman for the last two years and threatened to exclude his son (her husband) from his property if she disclosed (the matter) to anyone," police said.
An investigation has been opened into the case although no arrests have been made so far, they added.