In Mo'ed Katan (Bab. 20a) the Gemara relates a story about how Rav learned of the death of his parents from a conversation with R' Hiyyah. The Gemara tells us their relationship, and it's pretty critical to understanding the story that we know they are related through Rav's parents, but I just can't wrap my head around what the relationship is. It sounds like the Gemara is saying that Rav's parents were brother and sister. Can someone please clarify this for me?

1 Answer 1


והא רב בר אחוה דרבי חייא דהוא בר אחתיה דר' חייא

Rav, the son of the brother of R' Chiyya, was the son of the sister of R' Chiyya


דרבי אחא מכפרי נשא לאה והוליד ממנה אייבו מתה ונשא רחל ולה בת מאיש אחר וממנה נולד רבי חייא ונשא אייבו הבת ונולד להן רב ונמצא רב בר אייבו בר אחוה דרבי חייא מאבוה ובר אחתיה מאמיה

Rebbi Acha married Leah and had Ayvo. She died, he remarried Rachel and she had a daughter from a previous marriage, and from Rachel Rebbi Acha had Rebbi Chiyya. Then Ayvo married the daughter from the previous marriage and they had Rav. So Rav son of Ayvo is both the son of the brother and son of the sister of R' Chiyya.

              Leah -----Rebbi Acha ------- Rachel
                     |                |          \
                     Ayvo         Rebbi Chiyya    Daughter
                          \                         /
                           \ -------------------  /

So Ayvo married his step-sister, and Rav is related to R' Chiyya through his father and his mother, both as half-siblings.

  • 2
    There's a little part of me that's disappointed that Ayvo and Daughter had a kid before Ayvo died...
    – Double AA
    Sep 10, 2014 at 5:15
  • @yez, the way you translated it, it appears that "בר אחוה" is just the expression for "nephew", not an accurate description of their relationship (son of brother). If so, then maybe I just misread the Gemara (actually, the rabbi whose Shi'ur I was listening to also translated it as I did, rather than "nephew"). So what is the point of Rashi's explanation? And where does he get the family tree from?
    – Seth J
    Sep 10, 2014 at 16:07
  • @SethJ sorry the translation was a fossil from before I edited in Rashi. I updated to translate as it would read with Rashi. In terms of how Rashi knew (comment, as it isn't part of the question), he could be putting several things together - the gemara here is clear that Rav's father and mother were siblings of R' Chiyya. His father and mother could not have been siblings of each other, because then Rav would have been a mamzer. The only option left is two half-siblings. R' Chiya and Ayvo having the same father is Sanhedrin 5a, so the halves have to be from different mothers. As far as the... Sep 10, 2014 at 18:10
  • ...order of events, that R' Acha married Ayvo's mother and then R' Chiyya's mother, my suggestion is that the order in which the siblings are listed in Sanhedrin has Ayvo first, so he is assumed to be older, so R' Acha must have been married to Ayvo's mother and given birth to Ayvo before marrying R' Chiyya's mother and giving birth to R' Chiyya. Sep 10, 2014 at 18:12
  • As an aside, as far as the funny syntax of the Gemara here, I think it is because the gemara is referencing the line in Sanhedrin and quoting it verbatim as it appears there - והא followed by "רב בר אחוה דרבי חייא דהוא בר אחתיה דר' חייא" as Sanhedrin 5a is where the gemara identifies Rav as having that particular relationship to R' Chiyya, as opposed to the other nephews. Sep 10, 2014 at 18:18

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