Question: how can you be 1/3 of a race?
Answer: You can get really close to 1/3 or 2/3, but never exact. Ancestors come in powers of two. So you have 2 parents, 4 grandparents, 8 great-grandparents, etc. So the answer to this question is No, because there's no power of 2 that includes 3 as a factor.