In general, granddaughters and grandfathers are in the same household registration book, so it doesn't matter if the household registration books are different. The household registration number on the household registration book is given by the local police station, which is unique and will not cause any influence because it is on a household registration book. However, if your granddaughter goes to the police station for birth registration after birth, the police station will reprint a copy in the household registration book, so that the original grandfather's copy will be gone, which may have a certain impact on handling some matters involving the household registration book. Therefore, if you need to handle related business, it is recommended to bring your household registration book, ID card and other materials to the local police station for consultation.