Bank loans cannot be signed by family members. Just need the signature of the head of household. Buying a house with a loan is an important civil act, so usually the bank needs my signature for approval. If you need to sign, you must provide the corresponding legal documents. For example, the notarized power of attorney belongs to the guardian, and it is necessary to provide the proof documents of the guardian provided by the community and the public security organ. If the bank requires two people to sign at the same time, there is no other way. If the bank allows, it can sign on behalf of it.