Specifically what kind of relationships are defined as incestuous in Judaism? I am guessing that it is forbidden to marry one's parents/children or siblings but what about other relations like first cousins?

Also, what is the specific source (is this outlined Biblically or rabbinically)?

  • 5
    See Leviticus 18 and 20
    – Double AA
    Commented Jul 23, 2013 at 21:27
  • Cousins could get married, but today it's kind of gross.
    – A L
    Commented Jul 24, 2013 at 3:44
  • 1
    @AL Why is it gross? Commented Jul 24, 2013 at 5:49
  • 1
    Fixed Point, welcome to Mi Yodeya, by which I hope you're attracted, rather than repelled.
    – msh210
    Commented Jul 24, 2013 at 6:20
  • Let me echo @msh210's welcome and add that I hope you'll look around the site and find other material you can relate to, perhaps including our 180 other marriage questions.
    – Isaac Moses
    Commented Jul 24, 2013 at 11:39

1 Answer 1

  • Mother (B)
  • Mother's mother (R)
  • Mother's mother's... mother (R)
  • Mother's father's mother (R)
  • Father's mother (R)
  • Father's mother's... mother (R)
  • Father's father's mother (R)
  • Father's wife (B)
  • Father's father's wife (R)
  • Father's father's... father's wife (R)
  • Mother's father's wife (R)
  • Father's mother's father's wife (R; some permit)
  • Father's paternal brother's wife (B)
  • Father's maternal brother's wife (R)
  • Mother's brother's wife (R)
  • Sister (B)
  • Non-Jewish sister (R; some permit)
  • Daughter (B)
  • Daughter's daughter (B)
  • Son's daughter (B)
  • All further female direct descendants (R; some permit)
  • Wife's daughter (B)
  • Wife's daughter's daughter (B)
  • Wife's son's daughter (B)
  • All of wife's further female direct descendants (R; some permit)
  • Wife's mother (B)
  • Wife's mother's mother (B)
  • Wife's father's mother (B)
  • All of wife's further female direct ancestors (R; some permit)
  • Father's sister (B)
  • Mother's sister (B)
  • Son's wife (B)
  • Son's son's wife (R)
  • Son's son's... son's wife (R)
  • Daughter's son's wife (R)
  • Brother's wife (B)
  • Wife's sister while wife is alive (B)

(B = biblically prohibited, R = rabbinically prohibited)

Source: Shulchan Aruch Even HaEzer 15

  • 1
    Great answer (and +1), but you might want to add that one's niece is not a forbidden relationship - and was traditionally considered a good match. You didn't say that it was prohibited, but someone scanning the list might fail to notice that it's not mentioned.
    – Shimon bM
    Commented Jul 24, 2013 at 8:35
  • do the ellipses mean that it doesn't matter how many generations?
    – Menachem
    Commented Jul 24, 2013 at 12:52
  • @Menachem Yes.​​​​​​​​​​​​​​
    – Double AA
    Commented Jul 24, 2013 at 13:10

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