Very little has been tested yet, but the general thinking is that there’s probably no longer any generation cap, except for babies born since the new change went into effect a couple of weeks ago. The real trick is in proving it. From what I have read, the Canadian bureaucracy that processes these has usually asked for primary documentation, so actual birth certificates or centrally maintained religious records, and only once those have been exhaustively searched and the relevant local offices throw up their hands (via an official “we tried” letter) will they consider things like census forms and border-crossing logs.