Very little is actually written about St. Joseph of Nazareth, the husband and protector of the Virgin Mary and the adoptive father of Christ, and little is known of the past of this "just man". Still, his importance is well-recognized. He is venerated as a saint in the Catholic, Eastern Orthodox, Oriental Orthodox, Anglican, and Lutheran faiths. In Catholic and other traditions, he is the patron saint of workers and has several feast days. In 1870, Pope Pius IX declared him to be the patron saint and protector of the Catholic Church.
Similarly, the Virgin Mary. All we know about her is that she was a young peasant girl who was engaged to Joseph and (with her consent) experienced a Mystical Pregnancy. Beyond that, she doesn't have much characterization in the Biblical text itself; most of the popular interpretations of her character and appearance came from various theologians in the Catholic Church.
Serah is a two-scene wonder. In Genesis she is listed among Jacob's descendents going down to Egypt—notably, she seems to be the only girl among more than fifty grandsons. Later the Book of Numbers lists the various clans who left Egypt and, instead of mentioning her descendents, simply says "and Serah was the daughter of Asher." This has led to the interpretation that she lived through the whole, centuries-long Egyptian diaspora and returned to the Holy Land, spawning Jewish legends of her being immortal. Later unnamed women in the Bible, such as the Wise Woman of Abel, are sometimes said to be Serah.
From the Book of Esther, Xerxes' original queen, Vashti. Her only role is to refuse a summons to the banquet her husband was throwing (because, it is said, that he asked her to show up wearing only her crown) and to be subsequently divorced and deposed for it. (It is not known what happened to her afterwards.)
Another from the Book of Genesis: A Canaanite Priest King named Melchiezedek. He is noted for giving Abraham and Sarah some food and blessing them, and for acknowledging their God. Although it's not clear whether Melchiezedek was a true monotheist, or whether he merely worshipped El as the chief deity of a larger pantheon. He's sometimes considered to be an early stand-in for Jesus, especially since some deuterocanonical sources like the Dead Sea Scrolls portray him as a powerful angel, performing duties more commonly ascribed to Jesus (judging the dead) and Archangel Michael (battling Satan).
Classical Mythology has the snake god Ophion and the sea goddess Eurynome, a God Couple who are given an offhand mention in some version of the creation myth as briefly ruling the world between the Protogenoi and the Titans before being overthrown by the latter. They've prompted a great deal of speculation, including theories that they were the original heads of the pantheon before the violent suppression of their worshipers, hence their quick defeat in the recorded myth.