Faithful. Amidst the little we know of Joseph the husband of Mary, "faithful" is one word that can be attached to him with some degree of certainty. He that is faithful in that which is least is faithful also in much (Luke 16:10). Joseph was faithful to Mary. He was faithful to God. He was faithful to his family.
Faithful to Mary.
As her betrothed husband in waiting, Joseph was faithful to Mary. He maintained her purity (cf. Luke 1:34, e.g.) and his own. They did not engage in sexual relations before they were married. After discovering what (under normal circumstances) would have been betrayal of their betrothal, Joseph was disposed to act kindly toward his betrothed and not put her on public display (Matthew 1:19). As a new husband, Joseph protected Mary's virginity and Jesus's identity as a virgin born son by not consummating the marriage until after the birth of the Son of God. Like Joseph, many men have been called upon to raise some other man's child. Unlike any men, Joseph was called to raise God's child. This calling would include being the subject of gossip and innuendo. The "mathematicians" of Nazareth could certainly count the days from Joseph and Mary's marriage until the birth of her son! (Cf. John 8:41)
Faithful to God.
At least three times in Joseph's life he was visited by an angel with a message from God. Each time he faithfully obeyed. When Joseph considered putting Mary away for an act of infidelity, an angel presented the facts of a conception from God and not a man. This required Joseph to believe the unbelievable. But he believed and obeyed God, and took Mary to be his wife. After the birth of Jesus, an angel warned Joseph that the child Jesus's life was not safe in Bethlehem. Possibly not yet well settled after being displaced from Nazareth to Bethlehem, Joseph nevertheless believed God and uprooted his little family to life in a foreign country. There they must stay until they hear from God again. After Herod's death, Joseph received his third message from God in a dream -- return to Israel. And return he did. Each time God spoke in a message, Joseph responded in faithfulness.
Faithful to his family.
In all these incidents and more, we view a man who was a family man, faithful to his family. It was Mary who was chosen of God to bear the Saviour. In effect, Joseph was chosen as well. Joseph looked out for his wife. He looked out for the welfare of Jesus. He looked to the physical needs of his family, by working to supply for them (cf. Matthew 13:55). He looked to the spiritual needs of his family, by bringing them up according to the law of the Lord. Jesus was circumsised on the 8th day and given His name (Luke 2:21). They went to Jerusalem every year for the Passover (Luke 2:41). In only one recorded incident might Joseph be charged with not carefully fulfilling his duty as a parent, when Jesus was 12 years old and stayed behind in Jerusalem (Luke 2:43). But even then the Bible seems to place no condemnation, for Jesus was going about His Father's (God's) business.
Sometimes a man is called to a supporting role that is behind the scenes, out of the limelight and requires the faithfulness of decrease rather than increase. As Jesus grew in wisdom and stature, as His role "increased" the role of Joseph decreased. No longer needed is the man to care for his pregnant bride or her little newborn son. Whatever happened to Joseph as he fades into the background and then out of the picture, we may not know. But we may know this. When he is painted in the picture, when God tells us what he did, we find a man who was found faithful.
Moreover it is required in stewards, that a man be found faithful. (1 Corinthians 4:2)