What was the ethnic/cultural background of Justinian I?

Justinian I was one of the emperors of the Byzantine
Empire.  He ruled from 527 to 565 AD.  This put him a few decades after the fall of the
Western Roman Empire.

For someone who became emperor,
Justinian was of very humble background.  So much so that very little is known of his
youth.  What is known is that his parents were Macedonians -- people from an area in the
northern part of what is now Greece.  Justinian himself was born and raised in what was
then called Ilyria.  This is roughly the area that is now
Croatia.

Ethnically, then, Justinian was Macedonian. 
Culturally, he was Hellenic, since the Byzantine Empire was by that time very Greek in
its culture.