Why does Joseph appear in the Davidic genealogy of Jesus if God is his father?
Joseph is included in Jesus' Davidic genealogy because he was the legal father, not the physical father. Mary was the physical mother, and God was the father, but the royal Davidic line required Joseph's legal paternity to be recognized in the genealogy.
Les teaches that God gave David the promise that through him would come a royal family, the house of David. Even though ungodly kings came down through history, the royal blood kept together until the birth of Christ, especially through Mary, who was the physical mother. God is the father, but Joseph was the legal father, and so he too had to be included in that Davidic genealogy.