Halakhah su Levitico 18:7

To not reveal the nakedness of the father: That a man not reveal the nakedness of his father - meaning to say that he not lay with him, the layings of a woman, as it is stated (Leviticus 18:7), "The nakedness of your father [...] you shall not reveal." And this warning (negative commandment) about one who lays with his father is in addition to the general warning of laying with males about all men (Sefer HaChinukh 209), as it is stated (Leviticus 18:22), "And with a male you shall not lay, the layings of a woman." And so did they, may their memory be blessed, say in Sanhedrin 54a, "'The nakedness of your father [...] you shall not reveal' - your actual father." And they asked there, "That is extracted from, 'And with a male you shall not lay, the laying.'" And the one who answered, answered, "So as to make him liable for two [prohibitions], and it is like Rav Yehudah, as Rav Yehudah said, 'A gentile who has intercourse with his father is liable for two.'" And there they elucidated and said, "It is likely that the word of Rav Yehudah is with an Israelite, and inadvertent and with a sacrifice; and that which he said, 'a gentile,' is [because] he took a euphemistic expression." [This is] meaning to say that he did not want to mention this disgraceful matter with an Israelite, since it was possible to establish it with a gentile; as they are also commanded about sexual prohibitions, but the law is the same with an Israelite - that he is liable for two with his father, meaning that if he lay with him inadvertently, he is liable to bring two sin-offerings. The substance of this matter is revealed to all. There is no reason to be lengthy about its root, as it is fitting to distance this great ugliness from people, and to punish one who transgresses it [with] a great punishment. And therefore it made him liable for stoning.

To not reveal the nakedness of the mother: That a son not reveal the nakedness of the mother, as it is stated (Leviticus 18:7), "it is your mother, do not reveal her nakedness." About the reason for relatives, Rambam, may his memory be blessed, wrote (Guide for the Perplexed 3:49) that the matter is because the Torah distanced sexuality from people besides that which is needed for being fruitful and multiplying, or for the commandment. Therefore, the Torah forbade [close] relatives to us - as stumbling is found with them more, since they are always found (proximate). And Ramban, may his memory be blessed, said (Ramban on Leviticus 18:6) that this reason is very weak - that the Torah should make one liable for excision for one of these because of their being always found near him; and from another side, permit a man to marry one hundred women - or a thousand - if he wants. [Rather,] he, may his memory be blessed, said - and this is his language: "But according to logic, there is a matter of a secret from the foundations of creation this is implanted in the soul, and it is included in the 'secret of intercalation' (a play on words that can also mean conception), that we have already hinted to." To here [are his words]. And I have seen that Rambam, may his memory be blessed, wrote another reason about the matter (Guide for the Perplexed 3:49): From the angle of the simple understanding - according to my opinion - did he say [it is] because the Torah distanced [it], that he should not be brazen-faced to have intercourse with the woman that he is to treat with honor. And he pushes [it] to explain most of [the sexual prohibitions] from this angle, meaning to say on account of the trait of shame - all as it appears in his book; the matter would be [too] lengthy if we came to write it all.