If he is travelling to Canada to visit his sister, will that count as essential? If he does get his visitor visa and they get to travel tgt and quarantine tgt for 14 days will that still allow him to accompany her?
He will need to get authorization to travel as well as a TRV. The process is here under extended family member travel.
https://www.canada.ca/en/immigratio...vid19/visitors/immediate-family.html#extended
Impossible for any of us to say if it would be approved or not.