“Therefore the Lord himself will give you a sign: The virgin will be with child and will give birth to a son, and will call him Immanuel” Isaiah 7:14
This promise of Isaiah was fulfilled through Mary and Joseph. The gospels are clear that although Joseph took Mary home to be his wife, he was not the father of Jesus.
Jesus was fathered through the powerful working of the Holy Spirit. This miraculous conception meant that Jesus is the only person born without sin, thus qualifying Him to be the perfect sacrifice for your sin.