I really wish CIC could be consistent in what they want, after reading PMM's comment it reminded me of what i recall reading on this very subject, but it took me some time to locate the following text from the 2004 version of the CHC London checklist
Proof of relationship to your close relative in Canada (please include a family tree), such as birth, marriage or adoption certificates, proof of that person's status in Canada (as permanent resident or citizen) and their current address in Canada by submitting pay slips, tax documents, credit card receipts.
I know that they don't ask for all this in the current checklist, but it may help prevent being asked for more details later on if you prepare more information