Serbs were not considered Aryans by Germans but as subhuman, inferior races (Untermenschen) and foreign races that could not be considered part of the Aryan master race.
Untermensch (German pronunciation: [ˈʔʊntɐˌmɛnʃ], underman, sub-man, subhuman; plural: Untermenschen) is a term that became infamous when the Nazis used it to describe non-Aryan "inferior people" often referred to as "the masses from the East" like serbs and roma.
Serbs migrated to Europe in 6th century, They are from Carpathian Mountains near Russia and they are not authochthonous European.