Mary the mother of John Mark was one of the earliest of
Jesus's disciples. She was the sister of Barnabas (Col. 4:10), and joined with him in disposing of their land and giving the proceeds of the sale into the treasury of the Church (Acts 4:37; 12:12). Her house in
Jerusalem was the common meeting-place for the disciples there.
Initial text from Easton's Bible Dictionary, 1897 -- Please update as needed