Were Joseph and the Virgin Mary cousins?

Question

Scholar Bruce R. McConkie wrote:

Mary’s ancestors were the same as Joseph’s. She was a descendant through the royal line of King David. “Matthew says Joseph was a son of Jacob, and Luke says that he was a son of Heli. It appears, however, that Jacob and Heli were brothers and that Heli was the father of Joseph and Jacob the father of Mary, making Joseph and Mary first cousins with the same ancestral lines”

(Primary source: The Mortal Messiah, 4 vols. [1979–81], 1:316).

Matthew 1:16 states:

16 And Jacob begat Joseph the husband of Mary, of whom was born Jesus, who is called Christ.

Luke 3:23 is sometimes taken as a statement about Mary's lineage:

23 And Jesus himself began to be about thirty years of age, being (as was supposed) the son of Joseph, which was the son of Heli,

Were Jacob & Heli related, (potentially) making Joseph & Mary cousins?

Answer 1

The different genealogies of Matthew & Luke have spawned innumerable theories over the centuries. The proposal made by McConkie combines two older theories:

1. The common (but not universal) view that Matthew preserves Joseph's genealogy & Luke preserves Mary's.

2. The explanation provided by Sextus Julius Africanus, stating that Jacob & Heli were brothers. Africanus indicates that his source for this information is relatives of Jesus:

Matthan, who was descended from Solomon, begat Jacob. And when Matthan was dead, Melchi, who was descended from Nathan begat Eli by the same woman. Eli and Jacob were thus uterine brothers. Eli having died childless, Jacob raised up seed to him, begetting Joseph, his own son by nature, but by Law the son of Eli. Thus Joseph was the son of both. (as quoted in Eusebius, Ecclesiastical History 1.7)

If both propositions are true, McConkie's proposal follows from them. However, neither explanation (nor the many, many alternatives that have been written) can be decisively demonstrated from extant sources.

Were Joseph & Mary related? Probably yes. It is very likely both descended from David, and it is not unlikely that all Jews in Nazareth were related within several generations. However, we do not know from historical sources how closely related they were.