Jamieson, Fausset and Brown on Matthew 1:16

16. And Jacob begat Joseph, the husband of Mary, of whom was born Jesus--From this it is clear that the genealogy here given is not that of Mary, but of Joseph; nor has this ever been questioned. And yet it is here studiously proclaimed that Joseph was not the natural, but only the legal father of our Lord. His birth of a virgin was known only to a few; but the acknowledged descent of his legal father from David secured that the descent of Jesus Himself from David should never be questioned. See on Mt 1:20.

who is called Christ--signifying "anointed." It is applied in the Old Testament to the kings (1Sa 24:6, 10); to the priests (Le 4:5, 16, &c.); and to the prophets (1Ki 19:16)--these all being anointed with oil, the symbol of the needful spiritual gifts to consecrate them to their respective offices; and it was applied, in its most sublime and comprehensive sense, to the promised Deliverer, inasmuch as He was to be consecrated to an office embracing all three by the immeasurable anointing of the Holy Ghost (Is 61:1; compare Joh 3:34).