55. Is incest forbidden?
Yes, it is forbidden.
The nakedness of thy sister, the daughter of thy father, or daughter of thy mother, ... thou shalt not uncover. Leviticus 18:9
No, it is acceptable.Abraham married his half sister, Sarah. (Sarah and Abraham had the same father, Terah.) But God didn't mind. He blessed their union, her "a mother of nations."
And yet indeed, she [Sarah] is my [Abraham's] sister; she is the daughter of my father, but not the daughter of my mother; and she became my wife. Genesis 20:12Moses and Aaron were the products of an incestuous marriage. (Their father, Amram, married his sister, Jochebed.)
And Amram took him Jochebed his father's sister to wife; and she bare him Aaron and Moses. Exodus 6:20And Lot impregnated his daughters, while remaining just and righteous.
Lot ... and his two daughters ... dwelt in a cave. ... And the firstborn said unto the younger ... let us make our father drink wine, and we will lie with him, that we may preserve seed of our father. And they made their father drink wine that night: and the firstborn went in, and lay with her father; and he perceived not when she lay down, nor when she arose. And it came to pass on the morrow, that the firstborn said unto the younger, Behold, I lay yesternight with my father: let us make him drink wine this night also; and go thou in, and lie with him, that we may preserve seed of our father. And they made their father drink wine that night also: and the younger arose, and lay with him; and he perceived not when she lay down, nor when she arose. Thus were both the daughters of Lot with child by their father. Genesis 19:30-36