In the column of credit, there are two situations:
Without your parents' knowledge, he used your parents' certificate to get a loan. This kind of situation belongs to malicious deception, which violates the criminal law and will be investigated for criminal responsibility.
However, if your parents borrow money by proof, he will not bear the legal responsibility for repayment to the bank, and this responsibility will be borne by your parents. Your parents can get back the bank loan after they repay it.
If it is in the column of guarantor, the situation is different.