Jude wrote in the same era as Peter. In fact, much of the information in Jude is found also in 2 Peter 2.

Jude was the brother of James and the half-brother of Jesus. Both Matthew 13:55 and Mark 6:3 speak of James and Jude (along with Joseph and Simon) as brothers of Jesus. Though, according to John 7:5, Christ's brothers were not believers in him during his lifetime, these two at least became converts after his death.

James became a leader in the early church. We see him in action in 1 Corinthians 15:7, Acts 12:17 and 15:13, Galatians 1:19 and 2:9, 12, and Acts 21:18. We hear from Jude only in this book, except perhaps in 1 Corinthians 9:5. It is interesting to note that while Jude claims James as brother, both he and James refer to themselves as servants of Jesus.

The book of Jude was written to oppose false teachers who were sexually immoral and were teaching arrogantly. This letter would have been used as a sermon in the writer's absence (Craig S. Keener, The IVP Bible Background Commentary: New Testament [Downers Grove, Ill.: InterVarsity Press, 1993], pp. 752-53).