His wikipedia page says "Kerr is of Anglo-Indian descent. His father, Roger Kerr, was born in Calcutta, India, to an English father and an Indian mother." And there's a link in his dad's wikipedia page to an Age article which says
A few people in AFL circles used to think that Daniel was Aboriginal; more recently there have been stories printed that he is of Sri Lankan heritage. In fact he has family links to the British Raj and his grandmother was Indian.