I don't know of a way you can retroactively roll over the money. Chalk this up to a learning lesson. Here is guidance: Pros and Cons of Opening a 529 Plan for Each Child. This includes: You may use a single 529 plan account to save for more than one child as long as you change the beneficiary when it's time to pay for your next child's college expenses — at no cost. In most cases, it makes sense to have a separate 529 for each child, but some parents may prefer to use a single plan.
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