http://www.cic.gc.ca/english/informa...C.asp#overview
What must I do to obtain an Extended Stay?
In order to obtain an Authorized Period of Extended Stay Visa, you need to provide:
--- evidence of the parent or grandparent relationship to the Canadian citizen or permanent resident you wish to visit (e.g. birth certificate, baptismal certificate or other official documents naming you as parent),
--- a letter of invitation from your child or grandchild which includes arrangements for care and support,
--- proof from your child or grandchild that he meets the Low Income Cut-Off (LICO)
---
proof of that you have private medical insurance valid for a minimum of one year from a Canadian insurance company and that:
--- covers health care, hospitalization and repatriation,
--- provides a minimum coverage of $100 000, and
--- is valid for each entry to Canada and be available for review by a port of entry officer.