James was indeed the younger brother of Jesus. But Mark was not his disciple. In fact, Mark was a disciple of Peter, one of the original disciples of Jesus Christ. The Gospel according to Mark was written by him, who learned about the stories of Jesus through Peter and also Paul. He was an associate of Paul, who was the most revered and prominent preacher of the Gospel after the death of Jesus Christ. So, it is wrong that Mark was the disciple of James. Not only was he not that, he also did not learn about the stories of Jesus from James and did not retell the stories from James.
