'Father in law' in the Bible

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

While she was being brought out, she [took the things Judah had given her and] sent [them along with a message] to her father-in-law, saying, “I am with child by the man to whom these articles belong.” And she added, “Please examine [them carefully] and see [clearly] to whom these things belong, the seal and the cord and staff.”