Just like the children of siblings, the children of brothers-in-law and sisters-in-law are simply called nieces and nephews – clarified if necessary, whether “by marriage,” as opposed to “by blood” or “by adoption.” Brother-in-law or sister-in-law also refers to the reciprocal relationship between a person`s spouse and the spouse of siblings. In Indian English, this can be called co-siblings (specificity of a co-sister for the brother-in-law`s wife[2] or co-brother for the brother-in-law`s husband[3]). Thus, if one pair of siblings is married to another pair of siblings, the brothers-in-law and sisters-in-law are doubly related, each of the four by the spouse and the sibling couple, while the children of both couples are double cousins. A study examining the issue of envy in the triadic system of siblings, brothers-in-law, and spouses concluded that “sibling relationships have similarities to marital and sibling relationships” and that “relational closeness and satisfaction are correlated for all triad relationships.” [5] In Islamic law (Sharia)[6] and Jewish law (Halakha),[7] sexual relations between brothers-in-law and sisters-in-law are prohibited as incestuous unless the spouse is no longer married. Conversely, in Judaism there was the custom of Yibbum, according to which a man had the non-obligatory duty to marry the childless widow of his deceased brother so that she could have descendants of him. [8] Generally, a brother-in-law is the relationship between a person`s sibling and their spouse. This relationship is reciprocal because it includes the relationship between siblings and between siblings and between spouses. Most often, a brother-in-law is called brother-in-law for a male sibling and sister-in-law for a female brother or sister. [1] This term refers to siblings who have the same mother, but a different father or father, but have a different mother. Supported by Black`s Law Dictionary, Free 2nd ed., and The Law Dictionary.
One person is a brother “of all blood” for another, the first is a man if both are born of the same father and mother. He is a “half-blood” brother to that other (or half-brother) if both were born to different mothers or the same mother to different fathers of the same father. In civil law, the following distinctions are observed: Two brothers descended from the same father but different mothers are called brothers “related by blood”. If they have the same mother but are conceived by different fathers, they are called “uterine” brothers. If they have both the same father and mother, they are called “Germane” brothers. Siblings and sisters-in-law are bound by a type of kinship called affinity, like all relationships between in-laws. These are all relationships that are not directly related to the person through blood. [1] A rarer use of the term is observed in “casual conversations” with the term brother-in-law, which describes the relationship between the brother-in-law`s brother-in-law: William`s brother, Charles, has a brother-in-law named James (James is Charles` brother-in-law here not because he married his sister, but because he is a brother of Charles` wife), James referring to William as his brother-in-law. [4].