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  1. Who do you know would want to do that ?.

  2. Who do you know who would want to do that ?.

Consider the declarative version : You know who would want to do that. -> Interrogative version, which form by subject–auxiliary inversion should be 1 and it sound more natural to me.Why is there another "who" like in 2nd ?. When I search on google with the exact phrases,"who do you know would" vs "who do you know who would" , I get even more results with the latter.

gotube
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user2747502
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  • doesn't sound right. As for 2) I think I would say it "Who do you know that would want to do that?" but then its a duplicate that, although the second "that" would be easier to deal with.
  • – user3169 Aug 23 '14 at 17:58
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    Consider: 1. "You know [ [(that) Tom] / [who] ] would want to do that."; 2. "You know [ people / a person ] who would want to do that." – F.E. Aug 23 '14 at 21:22
  • They're both natural but mean different things. It's not possible to delete who from 2—that's not how 1 is formed. –  Sep 09 '14 at 12:07