This is how R. Yehudah explains the end of the Pasuk (K'naf Aviv - Refer to 23:1:2:3). See Na'ar Yonasan.
2)
What is the meaning of "Lo Yegaleh K'naf Aviv"?
1.
Rashi (like the Rabanan inYevamos 97a): It is a prohibition against being intimate with one's father's Shomeres Yavam
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(after the death of his [father's] brother).
2.
Ramban (in Ki Savo, 27:20): It means that one may not be intimate with the woman over whom his father spread a garment - married.
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3.
Yevamos 97a (according to R. Yehudah) and Targum Yonasan: It is a prohibition against being intimate with a woman whom one's father raped or enticed.
3
Having already taught the Isur of Eishes Aviv in Vayikra 18:8, why does the Torah need to repeat it here?
1.
Rashbam: To teach us - by virtue of its juxtaposition to "Lo Yavo Mamzer ... " - that, if one does marry her, the child born to them is a Mamzer,
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who is forbidden to marry into K'hal Hashem - and this extends to all Arayos.
2
Rashi writes that "K'naf Aviv" means his father's Shomeres Yavam. But the Torah already forbade Eishes Achi Aviv in Acharei-Mos, Vayikra 18:14?
1.
Rashi #1: To subject the son to a second La'av
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in the event that he transgresses.
2.
Rashi #2: To teach us - by virtue of its juxtaposition to "Lo Yavo Mamzer ... " - that a Mamzer comes only from [a Bi'ah of] Chayvei Kerisus'
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, but not from Chayvei La'avin.
