Here's the famous quote by Josephus that supposedly proves Jesus was real.
"And now Caesar, upon hearing the death of Festus, sent Albinus into Judea, as procurator. But the king deprived Joseph of the high priesthood, and bestowed the succession to that dignity on the son of Ananus, who was also himself called Ananus... Festus was now dead, and Albinus was but upon the road; so he assembled the sanhedrin of judges, and brought before them the brother of Jesus, who was called Christ, whose name was James, and some others; and when he had formed an accusation against them as breakers of the law, he delivered them to be stoned."
The relevant part is this: "and brought before them the brother of Jesus, who was called Christ, whose name was James,"
Now some speculate that this was about James the Just who would have been a bishop in the early Christian Church and not necessarily the blood relative brother of Jesus. So here's my thought. Even today priests, pastors and lay people call themselves brothers in Christ. If Jesus never existed as flesh and blood, and if he was known and thought of at the time as a celestial character like the Greek and Roman pantheon, isn't it possible that Josephus was describing James as a brother in Christ the same way a modern Christian might refer to pat Robertson as a brother in Christ?
This isn't the main quote used as evidence of Jesus' existence-that would be: "About this time there lived Jesus, a wise man, if indeed one ought to call him a man. For he was one who performed surprising deeds and was a teacher of such people as accept the truth gladly. He won over many Jews and many of the Greeks. He was the Messiah. And when, upon the accusation of the principal men among us, Pilate had condemned him to a cross, those who had first come to love him did not cease. He appeared to them spending a third day restored to life, for the prophets of God had foretold these things and a thousand other marvels about him. And the tribe of the Christians, so called after him, has still to this day not disappeared." The scholarly consensus is that the part about Jesus being "not a man" and the Messiah was a later Christian interpolation (since Josephus was known to not believe this, as Christian fathers such as Origen admitted-they also didn't mention this in their apologetic texts, meaning it was likely added later). So they do think he mentioned Jesus, but not as the Messiah. The mention of James is almost universally deemed authentic, along with one of John the Baptist (though it differs from the Biblical accounts).
There's actually significant speculation that the passage you quoted is a fabrication of Eusebius.