Really, and how is Jesus then of the lineage of Judah and David? Through Joseph?
Where does scripture indicate that Mary is of the Davidic line?
"Many early Christian sources refer to Jesus as a descendant of David (Matthew 1:1, Mark 10:47-48, Luke 1:32, Romans 1:3, Revelation 22:16), and Jesus seems to have accepted the claim (Matthew 12:22-32, 15:21-28, 21:1-16, Mark 10:46-52, 12:35-37). Since relatives of Jesus were available to and prominent in the early church and since some genealogical records were kept among the Jews of the first century, the early Christian accounts of Jesus’ being a descendant of David seem credible. Some of the earliest Christians had been active in the leadership of Judaism during the early stages of Christianity (Acts 6:7, Philippians 3:4-6), so they probably would have heard of objections to Jesus' Davidic ancestry if there were any. Paul, for example, was active in persecuting the church and surely would have had significant knowledge of the arguments used against Christianity by the earliest opponents of the movement, and he was in contact with Jesus' immediate family. He affirms Jesus' Davidic descent (Romans 1:3, 2 Timothy 2:8). How could Jesus' claim to be the Messiah have gotten far among so many people who had the expectation of Davidic descent, and why would He have even thought of Himself as such a Messiah in the first place, if He wasn’t descended from David? As the author of Hebrews indicates, information on Jesus’ background was "evident" to the public (Hebrews 7:14). Raymond Brown referred to Jesus' Davidic descent as accepted by "the majority of scholars" (The Birth Of The Messiah [New York, New York: Doubleday, 1999], p. 505). Craig Keener writes:
"there is little doubt that Jesus’ family historically stemmed from Davidic lineage. All clear early Christian sources attest it (e.g., Rom 1:3); Hegesippus reports a Palestinian tradition in which Roman authorities interrogated Jesus’ brother’s grandsons for Davidic descent (Euseb. H.E. 3.20); Julius Africanus attests Jesus’ relatives claiming Davidic descent (Letter to Aristides); and, probably more significantly, non-Christian Jewish polemicists never bothered to try to refute it (Jeremias 1969: 291). Jesus’ relatives known in the early church seem to have raised no objection to the claim of their family’s background (Brown 1977: 507)….B. Sanh. 43a, bar., may preserve a [non-Christian Jewish] tradition that Jesus was of royal lineage (unless it suggests connections with the Herodian or Roman rulers, or that he was about to take control of the people; both views are unlikely)." (A Commentary On The Gospel Of Matthew [Grand Rapids, Michigan: William B. Eerdmans Publishing Company, 1999], p. 75 and n. 9 on p. 75)
http://triablogue.blogspot.com/2006/12/son-of-david.html
It is stated in the Christian Gospels that Jesus was descended from David and has been Head of his dynastic house since birth, and is thereby the lawful King of Israel. Although Christian faith has it that Jesus was born of the Virgin Mary and, consequently, has no natural human father, he is nevertheless considered to be a Prince of Judah as though Mary's husband Joseph were in fact his father. According to Jewish law a man is presumed to be the natural father of every child his wife bears, unless the contrary is judicially proved. Alternatively he can unilaterally deny paternity, but not when he has already taken paternal responsibility for the child, such as by naming him.
Additionally, in many ancient cultures, including Israelites, genealogy was not considered the same as paternity. For instance, under the Mosaic law, if a man died without offspring and he had a brother, the brother was legally required to marry the widow and the dead brother was considered the father of their first child (Genesis 38). Under such broader views, Jesus could be the legal son of Joseph, and therefore be from the line of David, without being Joseph's biological son and without being adopted.
Also, the New Testament lists two different genealogies for Jesus, one at the beginning of Matthew and one in Luke 3:23-38. Matthew says "A was the father of B, B was the father of C", etc. Luke, however, uses a word that can mean either "biological son" or "descendant", in the form "C was the son of B, who was the son of A". Matthew shows a lineage from David, father of Solomon and Luke shows a lineage through Nathan, a son of David. A common explanation offered by Christian biblical scholars is that Matthew is stating Joseph's line and Luke is stating Mary's line. Under this interpretation, Jesus would be a biological descendant of David through his mother.
http://en.wikipedia.org/wiki/Davidic_line