"My Grand Aunt, lists his birth date as March 10, 1889. She also lists that he came to the USA when he was 16, that he was sponsered by a scientist named Pupin."
He was probably sponsored by the Serbian National Foundation in America, of which scientist MIHAJLO PUPIN was the president . Either your grand aunt or someone interpreting what she knows made a slight error there - Pupin and your ancestor were of common ethnic Serbian origin, not from the same area/village. :)
"In America, in 1909. MIHAJLO PUPIN established one of the oldest Serbian emigrant organization – Union of Serbs - “Sloga”. The organization had a mission to gather Serbs in imigration and offer help, as well as keeping ethnic and cultural values. This organization later merged with three other imigant societies.
Other emigrant organizations in to one large Serbian national foundation, and Pupin was one of its founders and a long time president (1909–1926))."http://en.wikipedia.org/wiki/Mihajlo_Idvorski_Pupin
Mihajlo Pupin had, besides that, been the benefactor of many other ethnic as well as his own private charities that sponsored children of Serbian immigrants in the US:
KOLO SRPSKIH SESTARA
SRPSKA NARODNA ODBRANA
Contact the current Serbian societies to see if there are any records like the ones that exist for the similar organization he sponsored in the old country - Serbian Trade Association "Privrednik" ( "The Merchant) :http://www.rodoslovlje.com/en/documentation/serbian-trade-as...
For info on these organizations and help with contacting them I recommend this lady and her awesome website on culture, heritage, traditions and life of ethnic Serbian immigrants: http://www.babamim.com/http://www.babamim.com/contact
*JOVIN* - your question regarding this : "Is Jovin the native spelling for Stephen?" - No, it isn't.
- Serbian language has a different grammar - there is something called grammatical case:http://en.wikipedia.org/wiki/Grammatical_case
*Jovin* - this is simply the first name JOVO spelled in case with different ending and additional meaning
*JOVIN* = * of JOVO*, as in
KRULJ DUŠAN JOVIN
KRULJ DUŠAN (son) of JOVO
"Rodoslovlje" Serbian Genealogy Societyhttp://www.rodoslovlje.com/en