'Father in law' in the Bible

Now his daughter-in-law, Phinehas’ wife, was pregnant, and was about to give birth; so when she heard the news that the ark of God had been taken and that her father-in-law and her husband had died, she kneeled down and gave birth, because her [labor] pains began.

And she named the boy Ichabod, saying, “The glory has left Israel,” because the ark of God had been taken and because of [the deaths of] her father-in-law and her husband.