was the birth of Christ announced to Mary, or was it announced to Joseph in Mt 1:20?
Both. It was first announced to Mary, since she would wonder why she was pregnant. Later, the angel gave the news to Joseph so that Joseph would not divorce Mary for unfaithfulness. See When Critics Ask p.381 for more info. Q: In the Gospels, what points do the infancy narratives have in common? A: Mark and John do not mention and details anything about Jesus birth. Here are six common points of Matthew and Luke: 1. Genealogy from Abraham to David (Mt 1:2-6; Lk 3:31-34) 2. King Herod was ruling (Mt 2:1; Lk 1:5) 3. An angel of the Lord visits (Joseph: Mt 1:20; Mary: Lk 1:26-38) 4. Jesus was born in Bethlehem of Judea (Mt 2:1; Lk 2:4-7) 5. The three of them returned to Nazareth. (Mt 2:19-22; Lk 2:39) 6. Jesus grew up in Nazareth. (Mt 2:23; Lk 2:40) In general, the two gospels dovetail beautifully to give a fairly complete picture of Jesus infancy. Matthew tells of Josephs genealogy, the wise men, and the flight to Egypt. Luke has Gabriel, John the Baptists birth, Marys genealogy, the she