How to be a good brother-in-law? Happy to full Meaning with Neay Kren Song

A brother-in-law (plural brothers-in-law) is the brother of one's spouse or the husband of one's sibling.

A sister-in-law (plural sisters-in-law) is the sister of one's spouse or the wife of one's sibling. Relative to a woman, the latter case (typically her husband's brother's wife; that is, the two women have married brothers) is occasionally called a 'co-sister-in-law', as they are each the sister-in-law of the other's husband.