No, the Bible prohibits marriage with any close relative, even your step-father's child.
"And if a man shall take his sister, his father's daughter, or his mother's daughter, and see her nakedness, and she see his nakedness; it is a wicked thing; and they shall be cut off in the sight of their people: he hath uncovered his sister's nakedness; he shall bear his iniquity," Leviticus 20:17.
"No one is to approach any close relative to have sexual relations. I am the LORD…Do not have sexual relations with your sister, either your father’s daughter or your mother’s daughter, whether she was born in the same home or elsewhere," Leviticus 18:6,9.
