Mark, of the New Testament was John Mark. His mother, Mary, was an important woman in the early church and he was a cousin or nephew to Barnabus. Mark appears first in Acts 12, where we learn of Herod’s persecutions. Herod killed James the brother of John with a sword and imprisoned Peter. However, Peter was rescued by an angel. After the angel departed, Peter went to Mary’s house, where many people, including Mark, were praying for Peter. He told them of his rescue by the angel, but then went somewhere else. Herod is subsequently killed and Barnabas and Saul returned from Jerusalem. They took Mark with them on their first missionary journey.
When the trio came to Perga in Pamphylia, Mark returned home for unspecified reasons. Later this would cause problems. When Paul and Barnabas were preparing to leave on their second missionary journey to check on the progress of their converts, Barnabas suggested taking Mark. However, Paul argued that since Mark had not been with them through half the journey, he should not go. This debate caused Paul and Barnabas to split up, each taking a different companion. Mark traveled with Barnabas, who, as mentioned before, was a relative. The two went to Cyprus by ship.
However, Paul and Mark appear to have worked out whatever differences they had, because Paul several times praises Mark in his letters. He asked Timothy to bring Mark with him to Rome, saying Mark was profitable to Paul in his ministry. Peter referred to Mark his son and mentions he is with Mark in Babylon, which was probably Rome. It is traditionally believed that this is where Mark wrote his gospel, using Peter as his source.
There is a tradition that after Peter died, Mark went to Egypt and founded the Church of Alexandria. Tradition also has him dying as a martyr.