'Brother in law' in the Bible

Then Judah said to Onan, "Go in to the wife of your brother and perform the duty of a brother-in-law to her, and raise up offspring for your brother."

"When brothers dwell together and one of them dies and has no son, the wife of the deceased shall not become the wife of a {man of another family}; her brother-in-law {shall have sex with her}, and he shall take her {to himself} as wife, and he shall perform his duty as brother-in-law [with respect to] her.

But if the man [does] not want to take his sister-in-law, then his sister-in-law shall go up to the gate, to the elders, and she shall say, 'My brother-in-law refused {to perpetuate his brother's name} in Israel, [for] he is not willing {to marry me}.'