Proof of relationship

[mariagw]

My aunt is a Canadian citizen but she was not issue with a birth certificate when she was born. Therefore, I am having trouble proofing that she and my mother have the same parents.

What are my options to establish that she is my aunt? Would a sworn affidavit be enough to establish proof of relationship? If so, how does one go about getting an affidavit in Vancouver, Canada?

Thanks.