If they lived with you all year, I'm assuming that you had them in school or visited a doctor with them at some point in the year. If so, go to the school or doctor's office and get a copy of your records showing that the kids lived with you. Alternatively, if they were on any form of government assistance while they lived with you, you can go to that office and request a copy of the records. Daycare records may also help if the kids were in daycare.
Also, here is the link for the TurboTax audit support center. Even if you didn't purchase Audit Defense, this may help you gather your records.
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