Self-taught ethnicity

Ethnicity: "Choose one box". It always stumps me! The results depend on choosing just one box, e.g. BMI --- you're either Asian or you're not. Living over 40 years without my mother's Cantoneseness, I began to construct my own Chineseness. After years of Australians asking me, "What country are you from?", despite never visiting China in my life, I now ironically feel I am a new type, a migrant's great-grand-orphan, who re-adopted the ancestor's country.