One common explanation for the divergence is that Matthew is recording the actual legal genealogy of Jesus through Joseph, according to Jewish custom, whereas Luke, writing for a Gentile audience, gives the actual biological genealogy of Jesus through Mary. This argument is problematic, however, because both trace their genealogy through Joseph. Eusebius of Caesarea, on the other hand, affirmed the interpretation of Africanus that Luke's genealogy is of Joseph (not of Mary), who was the natural son of Jacob, though legally of Eli who was the uterine brother of Jacob.