Usually you cannot use your family members’ visa cards in the UK.

Because a signature is required for credit card purchases in the UK, merchants must check whether the user's signature is consistent with the reserved signature on the back of the credit card, and some merchants will verify the user's identity.

Because in the UK, the division of responsibilities is more detailed, if the merchant fails to fulfill its verification obligations, the user can ask the bank to cancel the transaction at any time. So the UK usually checks information such as signatures.

If you use someone else's visa card, you may be found to have used it fraudulently. If the merchant finds out, it is not allowed to be used and may even take measures.