Your uncle being retired isn't a H&C reason. Nor is his being alone in Canada. And nor is your wanting to come to Canada.
H&C reason means there is some life or death situation involved, or some incredible hardship that would be faced if the H&C request was refused. It doesn't sound like this exists in your case, and in fact his having a fiancee and soon to be wife, would make the H&C claim even less viable.
Note that when he and his fiancee reach 1 year living together, or if they get married, that would immediately make him ineligible to sponsor you and any app in progress at that time would be cancelled.