Which Relatives Are You Prohibited from Marrying?
Leviticus’ list of conjugally-forbidden relations was extensive for its time. While the Karaites expanded the list greatly, the rabbis did so only slightly, leaving modern-day rabbinic Judaism with more relatives permitted for marriage than most western societies.
Published: May 1, 2019
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Last Updated: September 7, 2026
I am grateful to Dr. Mollie Lawee for sharing information about animal mating habits.
B. Hullin 114b. See Rashi’s commentary there, s.v. אחי פרדה: בן מותר עם אמו.
Baruch Levine, Leviticus, JPS Torah Commentary (Philadelphia: Jewish Publication Society, 1989), 254.
See detailed discussion in Eve Levavi Feinstein, “Sexual Prohibitions in the Bible and the ANE: A Comparison,”TheTorah.com (2018).
Gordon Wenham writes in his commentary to Leviticus: “The prevalence of the customs denounced here as Egyptian and Canaanite perversions is well attested in Scripture and in nonbiblical sources. In the Egyptian royal family, brothers married sisters. The laws of Hammurabi and the Hittites ban some of the incestuous relationships listed here, but by implication allowed other unions mentioned here.” Wenham,The Book of Leviticus, New International Commentary on the Old Testament (Grand Rapids: Eerdmans, 1979), 251. Modern scholars discuss whether the term “uncovering the nakedness” (לגלות ערוה) is a euphemism for sexual intercourse or for marriage. To me it seems that both are included in the term.
Tamar’s words in 2 Sam 13:13 also imply that she assumed that such a marriage was permitted, though the text never clarifies whether she is correct.
The half-sister is prohibited in Lev 18:9 and 20:17; it is also prohibited in Deut 27:22, as part of Deuteronomy’s much less extensive list. Marrying two sisters (when both are alive) is prohibited in Lev 18:18. Another example of a marriage that is narrated by the text with equanimity even though a later biblical text forbids it is Amram marrying his paternal aunt Yocheved (Exod 6:20), prohibited in Lev 18:12 and 20:19.
See, for example, Rashi’s comment to Gen 20:12 where he explains that Abraham married his paternal half-sister because בת אב מותרת לבן נח, a Noahide man is permitted to marry his father’s daughter (as long as the two of them do not have the same mother). See also similar arguments of Abarbanel (commentary to Lev 18) concerning the marriages of Jacob to two sisters, and of Amram to his aunt.
E.g. Levine, ibid.
See e.g. b. Yevamot 21a.
וזו אין לה הפסק . . . עד מעלה מעלה היא אסורה.
The apparent lacuna that seems most troubling is the lack of an explicit prohibition against sexual activity between a father and his daughter. The best answer to this problem is to note that, practically speaking, this lacuna is not real since the Bible specifically says (Lev 18:17):
עֶרְוַת אִשָּׁה וּבִתָּהּ לֹא תְגַלֵּה
Do not uncover the nakedness of a woman and her daughter
This verse effectively makes it forbidden for a man to have sexual relations either with his daughter or with his mother-in-law. Other explanations have been offered for this lacuna, and a vast literature exists that deals with the problem. See e.g., Jonathan R. Ziskind, “The Missing Daughter in Leviticus XVIII,” Vetus Testamentum 46.1 (1996): 126; Eve Levavi Feinstein, “Does the Torah Prohibit Father Daughter Incest?,”TheTorah.com (forthcoming 2019).
This expansion was necessary because the rabbis said that when the Torah forbade intercourse between a man and his father’s brother’s wife, the reference was only to a paternal brother. So the rabbis had to step in to forbid a man’s father’s maternal half-brother’s wife. See Maimonides, Mishneh Torah, Qedushah, Issurei bi’ah 2:2.
I am grateful to Professor Daniel Lasker for sharing information about Karaite law. For his own discussion of this topic on this site, see the personal status section in Daniel Lasker, “Biblical Exegesis as a Source of Jewish Pluralism: The Case of the Karaites,” TheTorah.com (2017).
For more detail on forbidden relations in early Karaite Judaism, see Leon Nemoy, “Two Controversial Points in the Karaite Law of Incest,” Hebrew Union College Annual 49 (1978): 247–65; Nemoy, Karaite Anthology: Excerpts from the Early Literature (New Haven: Yale University Press, 1952), 123–32; Aviram Ravitzky, תורת ההיגיון ותורת ההכרה במתודולוגיה ההלכתית של יעקוב אלקרקסאני: תרגום עברי של כתאב אלאנואר ואלמראקב מאמר ד, שערים א-ח, עם מבוא והערות, AJS Review 41.2 (November 2017), 1–32.
Leon Nemoy, “Karaites,” Encyclopedia Judaica, 2nd ed., 11:799. For more details on what relations are considered incest in Karaite Judaism, see the continuation of the EJarticle. See also Sefer ha-hinukh ma’ayan Hayyim (Ashdod, 1996) by the former chief rabbi of the Karaites, Hayyim ha-levi.
Contemporary Karaites permit these marriages. Rabbanite Judaism always allowed such marriages, but some of the most complicated discussions in the tractate of the Talmud that deals with levirate marriage, Yevamot, revolve around this and similar problems. See e.g. Mishnah Yevamot chapter 3 and the Talmudic discussions.
Nemoy, “Karaites,” 799.
Lasker, “Biblical Exegesis as a Source of Jewish Pluralism.”
See for example the list of forbidden marriages in the Anglican Church’s Book of Common Prayer.
In fact, a court in the United States recently shocked many people by ruling that the marriage of a man to his half-sister’s daughter was legal. See, “Marriage between uncle and niece is ruled legal by New York Court,” The Telegraph, October 29, 2014.
See also b. Yevamot 62b and Derekh Eretz 16–17.
רגיל הוא שחז”ל הופכים רשות למצוה להוציא מלבן של מינין. Tosefta ki-feshutah, vol. 8, Qiddushin (New York: Jewish Theological Society of America, 1973), 915.
See Tosafot Yevamot 62b, s.v. veha-nose et bat ahoto; Tosafot Yevamot 99a, s.v. safeq eshet ahiv. The question for the Tosafists is only whether such a union is as desirable as the union between a man and his sister’s daughter, not whether such a union is permissible.
