'Father in law' in the Bible

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

It was while she was being brought out that she sent to her father-in-law, saying, “I am with child by the man to whom these things belong.” And she said, “Please examine and see, whose signet ring and cords and staff are these?”