There is no record of Jesus’ genealogy through Mary. So how do we know that Jesus descended from the house of David?
Matthew (1:2-16) and Luke (3:23-38) each thought it important to record Joseph’s genealogy. The Navarre Bible commentary on Matthew’s Gospel explains why this is important:
Jewish genealogies followed the male line. Joseph, being Mary’s husband, was the legal father of Jesus. The legal father is on par with the real father as regards rights and duties . . . Since it was quite usual for people to marry within their clan, it can be concluded that Mary belonged to the house of David. Several early Fathers of the Church testify to this—for example, St. Ignatius, St. Irenaeus, St. Justin and Tertullian, who base their testimony on an unbroken tradition. (28-29)
There is also other evidence that Jesus was David’s descendant. For example, Paul tells us that Jesus “was descended from David according to the flesh” (Rom. 1:3).