Or there occur three reasons, by one of which the Evangelist was led. For either one Evangelist has mentioned the father by whom Joseph was begotten, but the other his maternal grandfather, or some one of his ancestors. Or one of the fathers mentioned was the natural father of Joseph, the other his father who had adopted him. Or after the manner of the Jews, when a man has died without children, the next of kin taking his wife ascribes to his dead kinsman the son whom he has himself begotten.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: Quæst. Ev. ii. qu. 5.