It happens all the time, an unmarried plan participant signs up for a retirement plan and designates their parents and/or siblings as their beneficiaries. They subsequently get married, have children, and never bother to update their beneficiary forms. They die and it becomes a huge mess, whether the plan is covered under ERISA or not.
So to avoid a mess, make sure that all participants for your plan are advised that it may be a good time to update their beneficiary forms or designate someone as a plan beneficiary if they haven’t done before.