The brother of Jesus and of James.

Attributed text(s).
Epistle of Jude 1.

Related text(s).
Catholic epistles.

Useful links.
Jude in the Online Encyclopedia.
Brethren of the Lord in the Catholic Encyclopedia.
The Relatives of Jesus (Richard Bauckham).
The Brethren of the Lord (Lightfoot).

Jude was the brother of Jesus and of James the just. He is mentioned in passing in Matthew 13.55 = Mark 6.3 as one of the four brothers of Jesus. His only other mention by name on the pages of the New Testament is in the greeting of his own epistle, Jude [1.]1; Paul the apostle also refers to certain unnamed brothers of the Lord in 1 Corinthians 9.5, and Luke mentions unnamed brothers of Jesus in Acts 1.13.

Jerome, On Famous Men 4:

Iudas frater Iacobi parvam, quae de septem catholicis est, epistolam reliquit; et quia de libro Enoch, qui apocryphus est, in ea assumit testimonium, a plerisque reiicitur, tamen auctoritatem vetustate iam et usu meruit, et inter sanctas scripturas computatur.

Jude the brother of James left a short epistle which is from among the seven catholic epistles; and because in it he borrows from the book of Enoch, which is apocryphal, it is rejected by many; nevertheless it merits authority now by its age and its use, and is reckoned among the holy scriptures.

Peter and the brothers of the Lord appear to share a certain connection in Acts 1.13-14; 12.17; 15 (passim); Galatians 1.18-19; 2.9-14; confer Matthew 28.10 = Mark 16.7; John 20.17; 2 Peter 1.1 (Simeon in א, A, and the Byzantine tradition; confer Simeon in Acts 15.14).