'Father in law' in the Bible

It was told Tamar, saying, "Behold, your father-in-law is going up to Timnah to shear his sheep."

When she was brought forth, she sent to her father-in-law, saying, "By the man, whose these are, I am with child." She also said, "Please discern whose are these -- the signet, and the cords, and the staff."