"A record of the genealogy of Jesus Christ the son of David, the son of Abraham."
The first verse of the New Testament tells us the baby born in the manger is the son of David who's the son of Abraham.
Now, who exactly was David? From the Old Testament we know that David was an adulterer, murderer, a polygamist, bad father, his hands were so bloody that God wouldn’t let him build the temple. His son Solomon did that. Solomon was a polygamist, a man full of futility and focused on pleasure.
He’s the son of Abraham. From the Old Testament we know that Abraham was a liar who disbelieved God and committed adultery. His son was Issac - a liar and idolater.
David and Abraham. Two sinners who’s seed was the son of God. One fathered the nation of the Messiah. One fathered the royal line.
Amazing what can happen when people who've done terrible wrong allow themselves to be used by God and take part is His greater plan.