After the due date of the tax return, the law does not allow changing a return from joint filing to married filing separate. You can only make the change from filing joint to filing separately if you file the corrected returns before the original due date of the tax return. Since the original due dates have long passed, your ex-spouse will not be able to change the filing status on the returns for those years.
I am giving you a link below to Form 1040X which is used for an amended return. Refer in the top section to Line C for filing status and see the notation.
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