afaik, bulgars cluster with greeks and romanians (balkan pops) more than with serbs or other south slavs. The bulgar elite (turkic) took on the slavic language/culture after one generation meaning that the slavic low nobility must've infiltrated alternatively that serbs intermarried.

Genetically they're thracian culturally slavic. Nevertheless, Dimitar Berbatov has contributed alot to Man U hehe.