According to the Gospel of Mark, Jesus had at least four living brothers and multiple living sisters when he started spreading his message. His named brothers were James, Joses, Judas and Simon.
In spite of what seems like a clear statement from Mark, the Christian church has long debated whether he really had siblings or if the scripture was referring to cousins or followers as brothers and sisters. The Catholic church usually taught that his mother Mary remained a virgin her entire life, a feat difficult to accomplish when giving birth to at least six other children. Some evidence supports this argument; the Greek word "adelphios" referred to both siblings and cousins, and it is possible that the siblings were the children of Mary's husband Joseph from a previous marriage.