Your disciple is not the first child of God to encounter unfair circumstances in his youth. Joseph, David, and Daniel all faced unjust situations as teens. Rather than becoming bitter towards God, by faith they embraced the goodness, love, power, and faithfulness of God in spite of their circumstances. (As I have written in other places, I believe God expects much from teenagers and often requires of them a faith that not even their parents understand.)

Recorded for us in Daniel Chapter 2 is a prayer Daniel prayed as a teenager. This prayer gives us insight into his deep trust in the nature and ways of God even though he was young and in the middle of life threatening conditions.

Praise be to the name of God for ever and ever; wisdom and power are his.
He changes times and seasons; he deposes kings and raises up others.
He gives wisdom to the wise and knowledge to the discerning.
He reveals deep and hidden things; he knows what lies in darkness,
and light dwells with him. (Daniel 2:20-22)

Here is how I approach bitterness with my disciple:

1. Use the lives of Joseph, David, and Daniel as a backdrop to talk through with your disciple his history to help him understand that God’s wisdom and grace takes this history, no matter how painful or unjust, and uses it for His glory and the fulfillment of His purpose.
2. Exhort your disciple to release God and others from his bitterness. There is no justification for the behavior of Joseph’s brothers toward him, but through the lens of faith Joseph was able to forgive and embrace his brothers and not hold their actions against them. (As Anne Lamott has said, “Not forgiving is like swallowing rat poison and waiting for the rat to die.” [1])
3. Bitterness, ingratitude, and discontentment are related and your disciple can counter these with thanksgiving. Have your disciple write out his points of bitterness (both circumstances and individuals) and then have him thank God for each of the situations.
4. The best dad, mom, siblings, education, body, brain, etc. for him to have are the ones he has.

[1] Anne Lamott, “Bird by Bird”, (New York: Pantheon Books, 1994)