James the Just, also called James the Greater, is usually said to be an “older brother” of Jesus, a son of Joseph by a previous marriage. James the Lesser is said to be either a younger brother or cousin. In all likelihood they were part of a cohort of students or near-relatives who called each other “brothers”.
According to the Book of Acts in the New Testament, James the Just took on the formation of a community in Jerusalem based on Jesus’ teachings, after Jesus was no longer around.
The name James comes from the Greek word iamos, which means “healer” (and became Iago in Spanish; hence Santiago meaning “Saint James”). Aramaic sources call both of these men Ya’acov, or Jacob, which is probably their given name and means “usurper, supplanter” referring to the Genesis story in which Jacob (who later becomes Israel) supplants Esau to receive his inheritance. Unfortunately, as a result, many people think that the name James means the same thing as the name Jacob.