James and John truly experienced suffering for Jesus. James died for his faith (Acts 12:1–5). John died an old man, having experienced persecution (Tertullian, The Soul 50; Jerome, Commentary on Galatians 6, 10).
Yet the death of James and John was not the same the death of Jesus. No believer can die the death of Jesus as a sacrifice for the world's sins (Mark 10:45) or experience the unique suffering he experienced on the cross (15:34).