Regarding Robert Eisenman's book called James the Brother of Jesus: The Key to Unlocking the Secrets of Early Christianity and the Dead Sea Scrolls https://en.wikipedia.org/wiki/James_the_Brother_of_Jesus_(book) says the following.
"The central claim is that Jewish Christianity emerged from the Zadokites, a messianic, priestly, ultra-fundamentalist sect, making them indivisible from the milieu of contemporary movements like the Essenes, Zealots, Nazoreans, Nazirites, Ebionites, Elchasites, Sabeans, Mandaeans, etc.
In this scenario, the figure of Jesus at first did not have the central importance that it later acquired. The canonical Twelve Apostles were no more than an artificially expanded replacement for the smaller circle of brothers of Jesus. After his crucifixion one of his brothers, James the Just took his place as the leader of this party, besides other factions loyal to Jesus (Ebionites) and to John the Baptist (Mandaeans). The central triad of the early Jerusalem Church will be composed by James, Peter, and John the Apostle. According to Eisenman, James was an important religious figure in his own right."
https://en.wikipedia.org/wiki/Robert_Eisenman says the following.
'As far as Eisenman is concerned, James the Just, the individual Paul actually refers to as either "brother of Jesus" or "the brother of the Lord",[59] is the historical character who exhibits the most in common with "the Teacher of Righteousness" pictured at Qumran and he considers that these events are the ones vividly portrayed in the Habakkuk Commentary. Historically speaking, it is this character who led the "Opposition Movement", including Essenes, Zealots, Sicarii, and/or Nazoreans – even Ebionites – and who, as “Zaddik" (צדיק), i. e., "the Zaddik of the Opposition Movement", about whom all these groups revolved until his death at the hands of the High Priest Ananus ben Ananus in 62 CE as described both in Josephus and Early Church literature.[60] For him, the popularity of James and the illegality of the manner of his death at the hands of the Herodians, establishment High Priesthood, and Pharisees in 62 CE set the stage for and possibly even triggered the First Jewish Revolt against Rome in 66–73 CE – to say nothing of the fire in Rome, not long afterwards which, aside from his probably having set it himself,[dubious – discuss][citation needed] Nero was reported to have blamed on "Christians".'