Q. Is there any historical evidence that the Blessed Mother had siblings?
A. Here’s a reply from Father Reginald Martin:
We have no historical evidence to describe the family of Jesus’ mother, but in St. John’s account of the Crucifixion we read, “Standing by the cross of Jesus were his mother and his mother’s sister, Mary the wife of Clopas, and Mary of Magdala” (Jn 19:25). The ancient writers did not employ the punctuation marks we are familiar with, so the second Mary in the list is sometimes considered to be Mary’s sister, although since the second century, readers have understood this second Mary to be sister-in-law to Jesus’ mother, whose brother was Clopas.
Another tradition, however, expressed in the Protoevangelium of James, written about A.D. 150, is quite clear that Mary was an only child. This text is not scriptural, although its author certainly knew the traditions expressed by St. Matthew and Luke. He states Mary’s elderly and wealthy parents lamented their childlessness. Her father-to-be was turned away from the Temple because he had no child. He spent 40 days in the desert, in solitary prayer and fasting; his wife did the same at home. Angels appeared to both, promising them a child. They welcomed Mary with joy, and presented her in the Temple when she was 3 years old.