Like most siblings, 12-year-old Onna Okeke and her 11-year-old brother, Toby, have a lot in common. For starters, they look alike, sharing many similar facial features. They both love the cold, snowy winters of Canada, where they live. But Onna and Toby have plenty of differences too. So where do the similarities and differences come from? What is it that makes each person so unique – even when they are siblings? Let's get to the bottom of this together.