Ambrose of Milan — as excerpted in the Catena Aurea on Luke 3:23-38

“Rightly as was supposed, since in reality He was not, but was supposed to be so, because Mary who was espoused to Joseph was His mother. But we might doubt why the descent of Joseph is described rather than that of Mary, (seeing that Mary brought forth Christ of the Holy Spirit, while Joseph seemed to be out of the line of our Lord’s descent,) were we not informed of the custom of the Holy Scripture, which always seeks the origin of the husband, and especially in this case, since in Joseph’s descent we also find that of Mary. For Joseph being a just man took a wife really from his own tribe and country, and so at the time of the taxing Joseph went up from the family and country of David to be taxed with Mary his wife. She who gives in the returns from the same family and country, shews herself to be of that family and country. Hence He goes on in the descent of Joseph, and adds, Who was the son of Eli. But let us consider the fact, that St. Matthew makes Jacob, who was the father of Joseph, to be son of Nathan, but Luke says that Joseph (to whom Mary was espoused) was the son of Eli. How then could there be two fathers, (namely, Eli and Jacob,) to one man.”