This “other disciple” was probably John himself. His acquaintance with Annas got him into the courtyard, and he was able to convince the servant girl to let Peter into the courtyard also. But when questioned, Peter denies being a disciple of Jesus.
Let’s not dismiss Peter as altogether cowardly. Remember, he had begun to fight back in the garden when they came to arrest Jesus. Peter was in a very awkward and dangerous situation, once again surrounded by those same people. They knew John was a disciple of Jesus. The presence of another disciple there might arouse suspicions about an escape plot.
For most of us, it has been true that we have denied Jesus in far less dangerous circumstances. You aren’t supposed to be violent, but you aren’t supposed to be silent either. When others are maligning Him and His modern day disciples, do you deny Him by your silence? Do you hope no one asks the question of you?
Could a court convict you by the company you keep? It is easy to identify with Christ during church time. But outside of the comfort zone, do the friends of Jesus, the enemies of Jesus, and those who are supposedly non-committal about Jesus know which side you are on?
Jesus knows you will be persecuted for proclaiming the truth about Him, and He doesn’t want you to hide the truth about yourself.