Psalm 51:5 and 58:3 demonstrate the sinfulness of an infant as soon as they be born. They are born with a sin nature. The Bible indicates that they are born not into God's family but into the family of Satan. Thus Jesus could say to the Pharisees:
"You are of your father, the devil."
Every unsaved person is of their father, devil, and thus needs to be born into the family of God. They are born into the wrong family. Therefore there is the necessity of a new birth; a requirement to be born again.
Why did Jesus need to be born of a virgin?
He needed to be born of a virgin so that he would be born without sin. For sin is passed down through the seed of a man. It is inherited. It is inherited through Adam. By Adam's sin death has passed upon all men, for all have sinned. We are all sinners because of Adam. We have inherited the sin nature of Adam. Jesus did not because he was born of a virgin. Thus he was sinless. He had no sin nature to combat.
I am not sure you are correct. Jesus did not say everybody was of the devil.
Matt 7:11 If ye then, being evil, know how to give good gifts unto your children, how much more shall your Father which is in heaven give good things to them that ask him?
Are these people saved? Then why did Jesus say they were evil?
Jesus did say to those who rebelled and would not listen to him that they were children of the devil. But to those who did listen he said that God was their Father. Notice Jesus first says they are evil, and then says "your Father which is in heaven".
Not trying to be controversial, but these are the words of Jesus himself.