The "brothers" of Jesus in the Pauline Epistles and the Historicity of Jesus

[T]he mention of “brothers” of the Lord, as in I Cor. 9:5 and Gal. 1:19, is to be understood [by Christ mythicists] in the sense of community brotherhood. Yet we are not told why Paul in the same context should not have included Peter and Barnabas in the brotherhood. Moreover brothers in the Lord not brothers of the Lord, is Paul’s mode of thought for the community relationship. These are typical examples of both the brevity and the method Drews [a mythicists] uses in disposing of the Pauline evidence. It is difficult to take arguments of this sort seriously, particularly when they are presented so briefly and with no apparent ground of justification except the preposition that a historical Jesus must not be recognized. (Shirley Jackson Case, The Historicity of Jesus: A Criticism of the Contention that Jesus never Lived, a statement of the Evidence for His Existence, an Estimate of His Relation to Christianity [Chicago: The University of Chicago Press, 1912;repr., Forgotten Books, 2015], 74-74; comments in square brackets added for clarification)