Two things are required of a family member of an in-Canada spouse or partner applicant. The relationship has to exist both when the application goes in and when it is decided, subject to the age lock-in in 25.1(1). And the request for that person to stay as a permanent resident has to be in the application from the start; you cannot bolt them on later.
128 The requirements with respect to a person who is a family member of a member of the spouse or common-law partner in Canada class who makes an application under Division 6 of Part 5 are the following: (a)subject to subsection 25.1(1), the person is a family member of the applicant both at the time the application is made and at the time of the determination of the application; and (b)at the time it is made, the application includes a request for the family member to remain in Canada as a permanent resident.