"And he saith unto them, Ye shall drink indeed of my cup, and be baptized with the baptism that I am baptized with: but to sit on my right hand, and on my left, is not mine to give, but it shall be given to them for whom it is prepared of my Father." (Matthew 20: 23)
James and John did not ask Jesus this question directly, but rather their mother brought them to Jesus and asked this request.
Pretty arrogant, huh? Well, the other ten disciples were definitely offended:
"24And when the ten heard it, they were moved with indignation against the two brethren." (Matthew 20: 24)
Jesus did not shame the sons of Zebedee, nor did he put off the concerns of the other ten disciples:
"Jesus called them unto him, and said, Ye know that the princes of the Gentiles exercise dominion over them, and they that are great exercise authority upon them. 26But it shall not be so among you: but whosoever will be great among you, let him be your minister; 27And whosoever will be chief among you, let him be your servant: 28Even as the Son of man came not to be ministered unto, but to minister, and to give his life a ransom for many." (Matthew 20: 25-28)
Many people read this passage, and right away they run to serve God.
Before we can serve, though, we must allow Jesus to serve us.
"A new commandment I give unto you, That ye love one another; as I have loved you, that ye also love one another." (John 13: 34)
"This is my commandment, That ye love one another, as I have loved you." (John 15: 12)
Now, what the mother of James and John requested was not close to what God the Father grants us. Mom wanted her sons to sit on Jesus' side.
God places us in His Son, giving us the same identity:
"But God, who is rich in mercy, for his great love wherewith he loved us, 5Even when we were dead in sins, hath quickened us together with Christ, (by grace ye are saved;) 6And hath raised us up together, and made us sit together in heavenly places in Christ Jesus:" (Ephesians 2:4-6)
Not only did God the Father bring us to life from death, redeemed us from sin to righteousness, but we have received the same standing, a new self in Christ.
Jesus was right in that He could not seat James or John on His right or life, since God the Father seated Jesus at His right hand (Ephesians 1: 22)
Yet God gave James, John, their mother, and all of us beyond what we could have asked or thought (Ephesians 3: 20), by seating us in Christ, and placing us at the Father's right hand.