Does his wife work? They could qualify for PGP based on her salary. Unfortunately I have a sneaking suspicion that with a 2 year old and a 6 months old she is also unemployed. They recently chose to have 2 very young children (2 and 6 months) so they must have been able to handle that on top of his illness given that you did not have PR and have no guarantee of being able to remain in Canada. You were likely not in Canada before she got pregnant with the 2nd child. A letter from a doctor does not guarantee your approval. If you are able to volunteer, etc. you are not his full-time caregiver. Have you secured health insurance for yourself since you are on a TRV? Given your age there is a high risk that Canada and your family would need to support the health needs of another individual on top of your son and perhaps his whole family if his wife is not employed. Your best chance of success is to show all the medical tasks you do that his wife is unable to do and will save the taxpayers money. It is unclear how disabled your son is but things like carrying your son, bathing your son, helping with cooking and cleaning, etc. Would be list of things you could include if your son needs help and why list things that his wife is unable to do so you have to do. You will also need to show how you will support yourself. Given that you never worked in Canada you will qualify for a very small amount from the government every month to live on. Creating another senior living in poverty is not going to benefit anyone. Your health will also factor into your approval. If there is a high likelihood your health may decline this creates more of a stress versus a help. I wish you the best but getting PR is not guaranteed.