Researcher John Armstrong has developed a theory of two Oswalds which is described in the following way by his associate Jim Hargrove:
"JFK researcher John Armstrong has shown that the Warren Commission combined the biographies of two different people to arrive at the classic legend of Lee Harvey Oswald. One was a Russian speaking youth, possibly the child of Hungarian parents. Mr. Armstrong notes that this person preferred to be called "Harvey." The other was a taller but similar looking boy with a Southern U.S. accent, born as "Lee Harvey Oswald," and who preferred to be called "Lee." Both youths became entangled at an early age in an American intelligence operation designed to give a U.S. identity to a Russian-speaking child. It was "Harvey" who traveled to Russia and was shot dead by Jack Ruby. It was "Lee" who framed "Harvey" for the assassination of JFK. The operation began when both "Harvey" and "Lee" were CHILDREN, but it probably did not become entangled in the plot to assassinate President Kennedy until the spring and summer of 1963."
This website offers several articles, including my own multi-part series, that attempt to refute Armstrong's theories.
Harvey and Lee-Part One: Introduction.
Harvey and Lee-Part Two: Polishing the Big Apple and Other Matters.
Harvey and Lee-Part Three: The Handwriting is on the Wall.
Harvey and Lee-Part Four: Nonsense in North Dakota.
Three Key Areas That Disprove the Armstrong Theory.
Also presented here is a fine piece by Dave Reitzes telling why he changed his mind about Armstrong's research.
Long Division: One Researcher, Ten Months, and Two Oswalds by Dave Reitzes.