Im Australian as its my place of residence and your nationality is 100% based on your physical location of permanent residence so if you have joint citizen ship and you spend a equal amount of time in both locations you can claim your nationality as both, otherwise dominance of living location really does define it.
Genetically (ie ancestry wise) my mums German and my dads Indian (my grandfather was also a conscripted member of the nazi war machine), and my mother immigrated here in the 70's and met my dad then as well**. He originally immigrated from Indian to Brittan when he was 10 with his sister and from Brittan to Australian in the 70s where he met my mum** as a bus conductor and 12 years later they made me

(born 82')
So i have direct blood relatives in Germany, Indian, Brittan & Australia and since my mum was part a of a huge family (13 kids), i also have relatives in Africa, Scotland and China that i know of (nieces, nephews etc).
So generally I like to call my self a child of the world (ie human) but my home and nationality is and probably always will be Australia
*Interesting that my grandfather on my mums side would have killed my grandfather on my dads side if they had ever met each other because of a ideology that was forced on him by fascists
**And who says Australia isn't a multicultural place.