Harry S Truman's middle name was "S". My wife's first and middle names are hyphenated (common in Asia), but her U.S. passport leaves out the hyphen and just lists two names. A few years ago, we had trouble with Delta Airlines not crediting flight miles because her "legal" name (according to DL) was "name name" while her SkyMiles account was "name-name". We finally had to send name change information to remove (albeit, incorrectly) the hyphen. Yet, DL reservations showed "namename" with no hyphen nor space.