The exemption letter PHAC would still be required to allow them to board the flight, without this letter they will not be allowed to board the flight despite of having valid travel visa. That's what my understanding is so far after researching and reading many posts so if we don't get this letter, then they will not allow neither immediate family member nor siblings, let me know if anyone think otherwise.
The process of PHAC is very tedious, the form that they are asking to get filled by doctor, I don't know and even think doctor will fill it, so not sure what to do..