We don't know much about Saint Joseph, the earthly father of Jesus, but the little we do know says a lot about fatherhood.
First, no father is perfect. If you recall from the Gospels, Jesus disappeared when He was 12. Joseph and Mary found Him later, teaching in the temple. I can only imagine what Joseph went through; I have a feeling he was not so worried about losing the son of God and redeemer, but worried about having lost his son.
Second, then, it takes more than genetics to be a father. Saint Joseph was Jesus' father without a strand of DNA in common. He accepted Him with love when an angel told him of Mary's pregnancy. He protected him during their flight from Herod, and he searched for his son that day around the temple. (And, as the joke goes, he is the only man to shout to his child "Jesus, where did you run off to!" without blaspheming.) Love in all its forms - protection, sacrifice, concern, devotion - is what makes a man a father.
Third and last, he taught Jesus. I'm sure he followed the tradition of the time and taught Jesus his trade; we ususally refer to it as carpentry, though building might be more accurate. Some scholars have suggested that Joseph, as a builder, would have worked more with stone than with wood, and that's fine with me. As simple as it is, compared with the theology his Son delivered in the temple, it is not to be overlooked.
Some twenty years after those lessons, it was with wood and stone that Jesus conquered death and built our home in Heaven.
Grazie, san Giuseppe