J. B. Lightfoot wrote a seminal essay titled “The Brethren of the Lord” in his 19th c. commentary on Galatians. The text of this valuable writing is available at philologos.org. This essay contains an excellent summary of the various options regarding the familial relationship between Jesus and his brothers (including James). It discusses the early evidence, including the opinions of the Church Fathers. For the most part, the scanned text looks great, but the Greek text does not display correctly. Check it out here: http://philologos.org/__eb-jbl/brethren.htm.