Stojkovich (son of Stojko) could be either a Croatian family name (for a Catholic family) or a Serbian family name (for an Orthodox family). Son of Stojko in Bulgarian would be Stojkov.
Stojko is a South-Slavic (Croatian, Bulgarian, Serbian) name. Merely, It is a translation of the Roman name Constantine (you can see it in the database). Other popular South-Slavic names also translations of Constantine are Stojan and Stoichko. As translations of Constantine (St. Constantine introduced Christianity in Europe and founded Constantinople/Instanbul), these names are uncommon among Muslims in Bosnia.