Jealousy is a common problem we humans face, and dealing with other human beings takes great wisdom and skill. In fact, getting along with other people seems to be one of the greatest challenges that God has given us. The book of Proverbs has much to say about relationships, and spending some time reading through this book of the Bible reveals much about how God wants us to conduct ourselves.
As for dealing with personal jealousy, the Bible reveals that uncontrolled jealousy causes people to become very mean spirited (Proverbs 6:34). By contrast, Jesus said we are to love our enemies and those who mistreat us (Matthew 5:44). We must set aside jealousy if we are to become part of God's family (verse 45).
Jealousy can originate from misperceptions as well as reality. Whatever the circumstances, we should always strive to follow God's advice. Some ways we can diffuse jealousy include minimizing areas in which we seem to be competing with others and respecting others for their unique gifts and efforts. Most people respond favorably if we give them some room and treat them kindly.
Due to the general nature of this question, we are unable to identify specific reasons why you may be jealous of the other person. Here, parents and other mature counselors may be able to offer specific advice.
It is sometimes difficult to act like a Christian and set aside jealousies. But if we follow God's instructions about how to live our lives, we will be successes in the areas that really matter.