This James is he who in the Gospels, and also in the Epistle to the Galatians, is called the Lord’s brother. For Mary the wife of Alphaeus was the sister of Mary the mother of the Lord; John the Evangelist calls her “Mary the wife of Cleophas,” probably because Cleophas and Alphaeus were the same person. Or Mary herself on the death of Alphaeus after the birth of James married Cleophas.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: e Beda