Frater, a term of relation between two male children, sprung from the same father, or mother, or both. Scaliger and Vossius derive frater from πατρός, for πατρός, which properly signifies a person who draws water in the same well; ἀδελφός, in Greek, signifying well, and ἀδελφοί, a company of people who have a right to draw water out of the same well. The word, it is said, came originally from the city Argos, where there were only a few wells distributed in certain quarters of the city, to which those of the same neighbourhood alone repaired.

By the civil law, brothers and sisters stand in the second degree of consanguinity; by the canon law they are in the first degree. By the Mosaic law the brother of a man who died without issue was obliged to marry the widow of the deceased. Deuter. xxxv. 7. The ancients applied the term brother indifferently to almost all who stood related in the collateral line, as uncles and nephews, cousins, and the like. This we learn not only from a great many passages in the Old Testament, but also from profane authors. Cicero, in his Philippics, says, Antonia was both wife and sister of Mark Antony, because she was daughter of his brother C. Antonius. And as to cousins, Tullus Hostilius, in Dionysius Halicarnassenus, calls the Horatii and Curiatii brothers, because they were sisters' children. The language of the Jews, Bishop Pearson observes, included in the name of brethren not only the Brothers strict relation of fraternity, but also the larger one of consanguinity. We are brethren, says Abraham to Lot, Gen. xiii. 8, whereas Lot was only his nephew. So Jacob told Rachel that he was her father's brother, Gen. xxix. 12, whereas he was only her father's nephew. This consideration has been urged with good advantage against the Antidicomarianites, who, from the mention made of the brethren of Jesus, John ii. 12, Matt. xii. 46, have impugned the perpetual virginity of the mother of Christ. Among us it is customary for kings to give the title of brother to each other; the unction in coronation being esteemed to create a kind of brotherhood. Nor is the custom modern. Menander mentions a letter of Cosroes king of Persia to the emperor Justinian, beginning thus: "Cosroes, king of kings, to the emperor Justinian my brother." Kings now also give the same appellation to the electors of the empire. In the civil law, brothers, fratres, in the plural, sometimes comprehends sisters; as Lucius et Titia, fratres; tres fratres, Titius, Marius, et Scia.

Foster-Brothers, those who have been suckled by the same nurse. The French call them fratres du lait, or brothers by milk; which is most properly used in respect of a person who had been suckled by a nurse at the same time with the nurse's own child.

Brother was also used by the writers of the middle ages for acomes, or governor of a province.

Brother is applied, in a less proper sense, to denote a person of the same profession; in which sense judges, bishops, priests, call each other brothers.

Brother is also a customary term by which priests of the same persuasion address one another; but it is more particularly used to denote the relation between monks of the same convent; as Brother Zachary. In English we more usually say Friar Zachary, from the French word frère, brother. Preachers also call their hearers my brethren, or my dear brethren. This appellation is borrowed from the primitive Christians, who all called each other brothers. But it is now principally used for such of the religious as are not priests; those in orders are generally honoured with the title of father, whereas the rest are only simple brothers.

Brother is also an appellation more peculiarly given to certain orders of religious.

Brothers of Arms, an appellation given to those who contract a kind of fraternity in war, obliging themselves to the mutual service and assistance of each other. In the military orders the knights are also called brothers. In the order of Malta there is a particular class who are called serving brothers, consisting of such as cannot give proof of their nobility. In Latin they are denominated fratres clientes.

Brothers of the Rosy Cross. See Rosicrucians.