You submit ideally your uncle's birth certificate, your mothers birth certificate bearing the same father and mother name. you then submit your birth certificate. I must also advise you that proving a relationship is important; it is also important to prove that he is right now in Canada. I wasted 2 months only because they asked me to submit evidence that my brother is actually present in canada. Credit card statements, pay slips, tax returns, utility bills, all these will help. Good luck to Ms. Driven
