We have a Non-Resident Alien that has a non interest income checking account. They have a child who has a savings account with our bank and is sixteen years of age The child doesn't have a SSN or a W8Ben. The parents have a ssn and no W8Ben.
One of the parents is on the account as a secondary owner.

Should we require a W8Ben on the minor or put the parents ssn on the account.

This is an excerpt from the W-8BEN instructions

Note. If you own the income or account jointly with one or more other persons, the income or account will be treated by the withholding agent as owned by a foreign person if Forms W-8BEN are provided by all of the owners. If the withholding agent receives a Form W-9 from any of the joint owners, the payment must be treated as made to a U.S. person.

W-8 BENs are for non-resident aliens (NRAs), regardless of whether they have an SSN or not.

I definitely agree - W8-BEN for all NRAs. To take it a little further in the CDD/KYC arena. If the parents have SSNs, I would suspect (but would want to clarify with them) that they have US income. If they are filing taxes, they would certainly want to list the child as a dependent; therefore, wouldn't the child have an ITIN?