'Father in law' in the Bible

His daughter-in-law, the wife of Phineas, was pregnant and close to giving birth. When she heard that the ark of God was captured and that her father-in-law and her husband were dead, she doubled over and gave birth. But her labor pains were too much for her.

She named the boy Ichabod, saying, "The glory has departed from Israel," referring to the capture of the ark of God and the deaths of her father-in-law and her husband.