Does Mathew 13:55 Affirm Jesus Had Brothers and Sisters?

Not if you mean “brother” and “sister” in the traditional bloodline sense, as if Mary the Blessed Mother had other children besides Jesus.

To be clear, this was not an issue at the time of the Protestant Reformation, as John Calvin, Martin Luther and others defended Church teaching in this regard. Which ironically means that modern Protestants have developed a doctrinal tradition that departs from what their religious forebears held.

The Old Testament shows that “brother” had a wide semantic range of meaning and could refer to kinsmen such as cousins. Lot, for example, is called Abraham’s “brother” (Gen. 14:14), even though, being the son of Haran, Abraham’s brother (Gen. 11:26–28), he was actually Abraham’s nephew. Similarly, Jacob is called the “brother” of his uncle Laban (Gen. 29:15). Kish and Eleazar were the sons of Mahli. Kish had sons of his own, but Eleazar had no sons, only daughters, who married their “brethren,” the sons of Kish. These “brethren” were really their cousins (1 Chr. 23:21–22).

In addition, Hebrew and Aramaic did not have a word for “cousin,” and so cousins were referred to as brothers and sisters, although people in the ancient Holy Land knew you were using the word equivocally.

For more information on this subject, including how Scripture otherwise affirms Mary only had one Child (Jesus), including through the witness of Jesus, Mary and the Scripture writers otherwise, please read our tract “Brethren of the Lord.”