No, Sasanian-era Zoroastrian texts quite literally say that
xwēdōdah (parent-child or sibling incest) is one of the most pious and holiest acts possible. From the
Encyclopedia Iranica article:
According to
Dēnkard 3.80, the three kinds of “linkage” (
ham-paywandīh) achieved in
xwēdōdah are “father and daughter,” “son and birth-mother” (
burdār), and “brother and sister” (ed. Dresden, p. [53]; ed. Madan, p. 73; tr. de Menasce, pp. 85-86). Similarly, the
Pahlavi Rivāyat gives the hierarchy of
xwēdōdah as one’s mother, daughter, sister, but the rules are complicated by the fact that one’s sister may also be one’s daughter (ed. Williams, chap. 8d). According to
Dēnkard 3.80, the linkage will be the more efficient the closer the relationship between the two is: “of the same species” (
ham-srādag), “closely connected” (
nazd-paywand), and
nabānazdišt, an Avestan term of uncertain meaning, but approximately “closest relatives” (ed. Dresden, p. [53]; ed. Madan, p. 73; tr. de Menasce, p. 86). The best
xwēdōdah is that by which a son sires a son-brother with his birth mother, because, having come from her body, he is nearer to his origin; thus offspring from siblings with the same parents is more valuable than when the parents are different......
Practicing
xwēdōdah cancels the most grievous sins and saves from hell (
Pahlavi Rivāyat, ed., Williams, chap. 8b1-3). According to the
Rivāyat of Ēmēd son of Ašwahišt, if someone is destined for hell, the milk and goodness of the divine
xwēdōdah he has performed will keep his soul away from hell, as if it were surrounded by a fortification (
Rivāyat 27, ed. Anklesaria, pp. 104-5; ed. Safa-Isfehani, 1980, pp. 189-92, 1997, pp. 176-79). In the
Mēnōy xrad, performing
xwēdōdah for the love of one’s soul is listed among the good deeds that lead to paradise (
wahišt;
Mēnōy xrad 36.12; ed. Anklesaria, p. 107), and, according to the
Pahlavi Rivāyat, if a person maintains a
xwēdōdah marriage for four years, he is assured of
Garōdmān or, at least, paradise......
The
Mādayān ī hazār dādestān, a Sasanian law code, also talks about incest as something that's clearly very normal:
MHD. 104.9-14: a man assigns a golden object to his wife and a silver one to his daughter. If he marries his daughter, the question arises whether she is entitled to both objects.
MHD. 105.5-10: a man has left the two parts of his grounds, one to his son’s first-born (if a boy?) and one to his daughter’s first-born (irrespective of gender). The son and daughter get married and have a daughter, then a son, and the daughter inherits first, since they can have only one first-born child.
And the
Rivāyat of Ādur-Farnbay son of Farroxzād, a book of Zoroastrian religious law, has entries discussing the necessity of a father violently raping his daughter:
RAF. 20.1-2: if a man “needs” (andar abāyēd) to marry his daughter or his sister and they do not agree, may he use violence (stahmb)? And if he does, will the merit of the xwēdōdah accrue to him? The legal authority says yes to both, but adds that, if the husband does not agree, then he is not authorized to do it, and, if he does, then it is a sin.
Zoroastrian incest isn't just a CK2 meme, it was very real.