A religious brother is a member of a Christian religious institute or religious order who commits himself to following Christ in consecrated life of the Church, usually by the vows of poverty, chastity and obedience. He is a layman, in the sense of not being ordained as a deacon or priest, and usually lives in a religious community and works in a ministry appropriate to his capabilities. A brother might practice any secular occupation. The term "brother" is used as he is expected to be as a brother to others. Brothers are members of a variety of religious communities, which may be contemplative, monastic, or apostolic in character. Some religious institutes are composed only of brothers; others are so-called "mixed" communities that are made up of brothers and clerics (priests or ministers, and seminarians).
As monasticism developed in the early days of Christianity, most monks remained laymen, as ordination to ministry was seen as a hindrance to the monks' vocation to a contemplative life. Guided by the Rule of St. Benedict, the main lifestyle they followed was either agricultural or that of a desert hermit. Various forces and trends through the Middle Ages led to the situation where monks were no longer following this manner of living. Instead, they were focusing primarily on the religious obligations of intercessory prayer, especially for donors to the monasteries. This was encouraged by a spiritual reliance among the general membership of the Catholic Church upon the prayers of monastics to achieve salvation.
One practical consequence of this situation was that the bulk of the physical work which needed to be done for the simple survival of the monastic community came to be done by men who volunteered their services on a full-time basis, and who followed a less severe regimen of prayer. Called donates or oblati, they were not considered to be monks, but they were nonetheless gradually accepted as members of the monastic community.
In other communities, a separate labor force of "lay brothers" or conversi was cultivated in order to handle the temporal business of the abbey. These men were professed members of the community but were restricted to ancillary roles of manual labor. A rigid class system emerged from this arrangement in which the clerics (priests and seminarians) exercised complete control over the lay brothers. In some cases, lay brothers received little or no formal education, could neither hold office nor vote within their communities, and were forbidden from passing from the lay to the clerical state. In its worst form, this class system resulted in a master-slave relationship between clerics and lay brothers. This inequality between two groups of vowed religious men was not addressed by the institutional leadership of the Catholic Church until the Second Vatican Council.
In the 17th century, education of the poorer classes began to be seen as a means of providing charity, which had always been a mandate of Christianity. A leading figure of this approach was St. Jean Baptiste de la Salle, a canon of Reims cathedral, who began to help the poor children of the city. As he was gradually drawn into education as a means for this purpose, he established a new congregation of men for this work, who were called the Institute of the Brothers of the Christian Schools. De la Salle had initially intended the Institute to be composed of both ordained and lay members, but the death of the candidates he sent to Rome for ordination while en route convinced him to keep the Institute composed only of laymen. Thus the establishment of a recognized status of "brother" as other than an agricultural laborer came to emerge in the Church.
The social devastations of the 18th and 19th centuries saw the gradual emergence of other similar congregations of men, dedicated primarily to education. Other examples of such congregations are the Marist Brothers, the Brothers of Holy Cross, the Institute of the Brothers of the Christian Schools (also known as the De La Salle Brothers), Brothers of Christian Instruction of St Gabriel (Gabrielites) and the Congregation of Christian Brothers.
Since the Second Vatican Council (1962-1965) many brothers have moved toward professional and academic occupations, especially in the areas of nursing, education, peace, and justice. Brothers in communities with priests and seminarians often undertake advanced studies and enjoy equal standing with ordained members. Today, most brothers in the United States serve in some type of professional, technical, or academic ministry. Many serve as chaplains or teachers/faculty members at schools and universities run by their respective orders. In addition, most brothers undertake some studies in spirituality, religious studies, and theology.
Today there are more opportunities than ever for brothers in the Church. Brothers can be members of congregations that are made up only of brothers or they may belong to so-called "mixed" communities that include seminarians and priests. These congregations may be primarily contemplative or apostolic in nature; many try to balance both aspects of religious life. Brothers in the United States and elsewhere have access to an advanced education that is suited to their interests and talents. In mixed communities, brothers may collaborate with seminarians and priests or may minister independently of them. Brothers share equal status and rights with seminarians and priests in their communities with the exception that canon law currently requires that mixed communities elect an ordained minister as provincial; however, some dispensations to this rule have been granted. Brothers may be elected to provincial councils and other leadership positions.
The most acceptable term currently for the brother's vocation is "religious brother", and the vocational title is "Brother," sometimes abbreviated as "Bro." or "Br." The generic use of the term "brother" to describe fraternal or spiritual relationships between men in communities can sometimes lead to confusion about what it means to be a "brother" (religious). According to canon law, brothers are neither "lay nor clerical" but instead belong to the religious state of life. Hence, the vocational title "brother" is generally not used by seminarians (other than in monastic or mendicant Orders) in order to avoid the impression that being a brother is a developmental phase of clerical formation. However, as equal members of the same community, both priests and brothers would consider themselves brothers in the fraternal, communal sense of the term.
The term "lay brother" is considered offensive by some brothers since the word "lay" was once interpreted in this context to mean "illiterate" or "uneducated". However, in canon law it simply means "not clerical" or "not ordained".
Religious brothers who have been canonized as saints include:
- Alphonsus Rodriguez, S.J., porter
- Bernard of Corleone, O.F.M. Cap.
- Conrad of Parzham, O.F.M. Cap.
- Crispin of Viterbo, O.F.M. Cap.
- Didacus of Alcalá
- Felix of Cantalice, O.F.M. Cap., who was the first Capuchin friar to be canonized in the history of the Order
- Francis Mary of Camporosso, O.F.M. Cap.
- Gerard Majella, C.Ss.R.
- Ignatius of Laconi, O.F.M. Cap.
- St. John of God, Brothers Hospitallers of St. John of God
- St. Juan Macias, Order of Preachers
- Richard Pampuri, Brothers Hospitallers of St. John of God
- Martin de Porres, Order of Preachers
- André Bessette, C.S.C., Canadian founder of St. Joseph's Oratory in Montreal
- René Goupil, S.J. missionary and martyr/saint
- Albert Chmielowski, Polish founder of a congregation of brothers and another of religious sisters of the Third Order Regular of Saint Francis, which both bear his name.
- Bénilde Romançon, F.S.C., a French educator, who was the first member of his religious institute to be canonized
- Martyrs of Turon, eight Spanish Brothers of the Christian Schools executed during the Spanish Civil War
- Jaime Hilario, F.S.C., executed during the Spanish Civil War
- Miguel Febres Cordero, F.S.C., an Ecudorian educator
- Mutien-Marie Wiaux, F.S.C., a Belgian educator
- Paschal Baylon
- Isidore De Loor, Passionist, a Belgian brother
- Edmund Ignatius Rice, founder of the Congregation of Christian Brothers and Presentation Brothers
- Dominic Collins, Society of Jesus
- José Olallo, Brothers Hospitallers of St. John of God
- Redemptus of the Cross, Order of Discalced Carmelites
- Fra Angelico, Order of Preachers
- István Sándor, Society of St. Francis de Sales
- Henri Verges  , Marist Brother
In the Methodist Church, those who are called "Brothers" (Br.) are male monastics (e.g. votarists of Saint Brigid of Kildare Methodist-Benedictine Monastery) or members of a Methodist religious order (e.g. Order of Saint Luke).
All baptized members of Jehovah's Witnesses refer to other members in good standing as "brothers" and "sisters".