But doesn't IRCC says parents - Immediate family and Siblings - Extended familyImmediate family - Parents, Grandparents, siblings, children
Family - Cousins, Aunts and Uncles. Distant relatives.
https://www.canada.ca/en/immigration-refugees-citizenship/services/coronavirus-covid19/visitors/immediate-family.html
I'm little hesitant to go for Authorization Request letter from IRCCfor extended family since it's using webform and it would take a lot of time and energy. Did you do that?