You mean how to write a certificate to the notary office when your grandparents helped take care of your niece after your daughter died? According to the law of searching Baidu in the Internet, you can write like this:

1. Write down the basic information of the customs broker.

2. Write clearly the content of support.

3. Write down the time clearly and sign it by the applicant.

This is to certify that XXX (one of my grandparents) is the guardian of XXX (my niece) and is responsible for taking care of XXX's life after her daughter's death. This is to certify that.

This notary hereby solemnly declares that the contents involved in this certificate are true, accurate and complete, and there are no false or misleading statements or omissions.

Notary: XXX Notary Office: XXX Date: XX, XX, XX, XX.

Legal basis: Article 1074 of the Civil Code of People's Republic of China (PRC) stipulates that grandparents who have financial means have the obligation to support their minor grandchildren whose parents are dead or whose parents are unable to support them.