Brother

Brother in Scripture designates biological siblings (Matt. 1:2), near kinsmen such as nephews and cousins (Gen. 13:8; 14:16), fellow members of the covenant community (Deut. 15:3; 17:15), and members of the same tribe or nation. The broad semantic range of the Hebrew ach reflects a social world in which clan and kinship identity extended well beyond the nuclear family. Jesus' brothers mentioned in the Gospels (Matt. 13:55; Mark 6:3) have been variously identified as biological sons of Mary and Joseph, sons of Joseph by a prior marriage (the Epiphanian view), or cousins (Jerome's view), without final resolution.

In the New Testament, “brother” becomes the standard designation for fellow believers (Acts 9:17; Rom. 8:29; Heb. 2:11–12). Jesus' declaration that whoever does the will of God is his brother, sister, and mother (Mark 3:35) redefines kinship around spiritual allegiance rather than biological descent. Paul's description of Christ as “the firstborn among many brothers” (Rom. 8:29) places the resurrected Lord as the elder sibling of a new family constituted by adoption through the Spirit. The ethical obligation flowing from this brotherhood—including mutual forbearance, financial sharing, and the pursuit of one another's good—is a consistent theme of the NT epistles.