'Brother in law' in the Bible

“When brothers live on the same property and one of them dies without a son, the wife of the dead man may not marry a stranger outside the family. Her brother-in-law is to take her as his wife, have sexual relations with her, and perform the duty of a brother-in-law for her.

But if the man doesn’t want to marry his sister-in-law, she must go to the elders at the city gate and say, ‘My brother-in-law refuses to preserve his brother’s name in Israel. He isn’t willing to perform the duty of a brother-in-law for me.’