[quote=@Andreyich]
[@VoiD]
I'm having troubles finding suitable titles for my lad, would it be acceptable for me to say when his family moved to Constantinople they kept the Norse/Varangian title of "Lendmann?"
[/quote]

You could, but it would be pretty meaningless to the Empire's court - the Norse were seen as barbarians to even the Frankish kingdoms at the time, so you can imagine their noble titles weren't held in the highest esteem in the Empire. Perhaps [url=https://en.wikipedia.org/wiki/Byzantine_bureaucracy_and_aristocracy]this resource[/url] will help you?

EDIT: Your family could also be minor landholders, such as [url=https://en.wikipedia.org/wiki/Dominus_(title)]this.[/url]