Contradiction with Genesis 20:12
Abraham claims Sarah is his sister and wife, a familial relationship similar to what is prohibited in Leviticus 18:12.
Genesis 20:12: And yet indeed [she is] my sister; she [is] the daughter of my father, but not the daughter of my mother; and she became my wife.
Contradiction with Genesis 29:18-30
Jacob marries two sisters, Leah and Rachel, which is not in accordance with the prohibitions in Leviticus 18.
Genesis 29:18-30: And Jacob loved Rachel; and said, I will serve thee seven years for Rachel thy younger daughter.
Contradiction with 2 Samuel 13:13
Tamar speaks of shame in the act with her brother Amnon, which aligns with the prohibitions but contrasts with past narratives involving close kin.
2 Samuel 13:13: And I, whither shall I cause my shame to go? and as for thee, thou shalt be as one of the fools in Israel. Now therefore, I pray thee, speak unto the king; for he will not withhold me from thee.