Who, exactly, are James son of Alphaeus and Judas the Son [Brother] of James?

One note specifically is that some translations read that Judas (not Iscariot) was known as Judas **brother** of James, but most say Judas **Son** of James. Luke 6:16 **NIV** > Judas *son* of James, and Judas Iscariot, who became a traitor. Compare that to: Luke 6:16 **KJV** > And Judas the *brother* of James, and Judas Iscariot, which also was the traitor. So, who were the apostles named Judas and James son of Alphaeus, exactly? If these apostles were brothers, wouldn't they share the same father? James is known as James son of Alphaeus... Luke 6:15 NIV > Matthew, Thomas, James son of Alphaeus, Simon who was called the > Zealot, In Jude, the author also introduces himself as the brother of James Jude 1:1 **NIV** > Jude, a servant of Jesus Christ and a brother of James, However, this can also be Judas the brother of Christ and James, also the brother of Christ, but not necessarily the original apostles named Judas and James. I ask because today at study, the individual giving the study was positing that Judas brother/son of James and James were both brothers of Christ, whereas I have it understood that none of Christ's brothers came to faith in him until the post-resurrection appearances. Any help is appreciated!