529 owned by a grandparent..does the beneficiary child have any "rights" to the money?

[BelknapPoint]

Depending on how the account was set up- your mom could either designate a contingent owner (which logically would be either your dad or you) OR the account would/could revert to the beneficiary, I.e. your kid.

For the sake of clarity, I don’t think “revert” is the right word here, because unless the beneficiary was ever the legal owner of the account (and the facts here don’t indicate that), there is no beneficiary ownership status to revert to.

Do not assume. It’s worth checking…it would be in the original paperwork, or a quick call to the financial company where the account is held would likely yield the answer. People don’t always retain the original forms, but the brokerage firm where the account is would have a record of either a contingent owner, or what the particular plan’s rules are for when a 529 account owner passes before the money is used…

Because of privacy concerns, unless the OP or the beneficiary is designated as the contingent owner, I would be surprised if the account administrator discloses anything.