Answer your question. First of all, this card belongs to your family, and the bank rules forbid you to use it. But there is nothing wrong with using it in real life. As for the signature, it must be your family name. Because this signature should correspond to the Chinese phonetic name on the front of the card and be consistent with the signature handwriting on the blue of the personal signature on the back of the card. But in some cases, the cashier won't check the handwriting at all. Generally, they think the password is correct. However, comics without consumer passwords often check their handwriting carefully.

Let me give you a suggestion. He may need your family's card in the future. If you sign your name on the back of the card, it will remain unchanged for his future use. So it's better to ask him to help you with a negative card, which is more convenient and safe.