"In those days a decree went out from Caesar Augustus that all the world should be registered. This was the first registration when Quirinius was governor of Syria. And all went to be registered, each to his own town. And Joseph also went up from Galilee, from the town of Nazareth, to Judea, to the city of David, which is called Bethlehem, because he was of the house and lineage of David, to be registered with Mary, his betrothed, who was with child. And while they were there, the time came for her to give birth. And she gave birth to her firstborn son and wrapped him in swaddling cloths and laid him in a manger, because there was no place for them in the inn." --Luke 2:1-7 Luke 2: 10-11 "...the Angel said unto them, Be not afraid: for behold I bring you glad tidings of great joy, that shall be to all people (for) unto you is born a Savior, which is Christ the Lord."
The Son of God who is the true God became man, subject to all miseries except sin in order to have men for His sons. And how could He have men for His sons unless His only begotten Son had become man and thus brother to them? (Hebrews 2)