Josephus on Jesus may, or may not, have information useful in understanding the meaning of "James, the Lord's brother" in Gal 1:19. But this is a highly debated passage (see Carrier vs McDonald beginning at 1:36:20 https://www.youtube.com/watch?v=X1_ZEVDC7rw). Arguably, it is striking that there is another man named "Jesus" in the near context. I assume Jesus existed, so I do not agree with Carrier on that. But I do think that as a historian, Carrier makes a compelling argument in his reading of this text. What happens to the story as a whole if the Christian part underlined was interpolation?
...But this younger Ananus, who, as we have told you already, took the high priesthood, was a bold man in his temper, and very insolent; he was also of the sect of the Sadducees, who are very rigid in judging offenders, above all the rest of the Jews, as we have already observed; when, therefore, Ananus was of this disposition, he thought he had now a proper opportunity [to exercise his authority]. Festus was now dead, and Albinus was but upon the road; so he assembled the sanhedrim of judges, and brought before them the brother of Jesus, who was called Christ, whose name was James, and some others, [or, some of his companions]; and when he had formed an accusation against them as breakers of the law, he delivered them to be stoned: but as for those who seemed the most equitable of the citizens, and such as were the most uneasy at the breach of the laws, they disliked what was done; they also sent to the king [Agrippa], desiring him to send to Ananus that he should act so no more, for that what he had already done was not to be justified; nay, some of them went also to meet Albinus, as he was upon his journey from Alexandria, and informed him that it was not lawful for Ananus to assemble a sanhedrim without his consent. Whereupon Albinus complied with what they said, and wrote in anger to Ananus, and threatened that he would bring him to punishment for what he had done; on which king Agrippa took the high priesthood from him, when he had ruled but three months, and made Jesus, the son of Damneus, high priest.
2. Now as soon as Albinus was come to the city of Jerusalem, he used all his endeavors and care that the country might be kept in peace, and this by destroying many of the Sicarii. But as for the high priest, Ananias he increased in glory every day, and this to a great degree, and had obtained the favor and esteem of the citizens in a signal manner; for he was a great hoarder up of money: he therefore cultivated the friendship of Albinus, and of the high priest [Jesus], by making them presents; he also had servants who were very wicked, who joined themselves to the boldest sort of the people, and went to the thrashing-floors, and took away the tithes that belonged to the priests by violence, and did not refrain from beating such as would not give these tithes to them. So the other high priests acted in the like manner, as did those his servants, without any one being able to prohibit them; so that [some of the] priests, that of old were wont to be supported with those tithes, died for want of food.
https://en.wikisource.org/wiki/The_Anti ... #Chapter_9
