Such questions are made for enhancing your creative writing skills and so, you should attempt them on your own. However, here are a few points that will help you frame your answer.
- In your first few dialogues, explain your partner the situation of your brother.
- Either you or your brother should talk this out with that student who bullies (that why is the friend behaving this way?)
- If he still persists to bully your brother, you can complain to the coach of the team (or the principal).
- Make your brother understand that it is necessary to talk to his friend.
Hope this helps:)