They tell me that their records are confidential and they also need to know why I want the certificate. It's bonkers.
In Poland these records are closed for 100 years after the books close. Since the places of their births are now across the border in Ukraine and Belarus, you might have better luck checking in the archives there. If they are there, you should be able to get them. The other issue you raise is the bureaucratic circle you experienced. It is quite common when dealing with the bureaucrats and a government that chooses to ignore the effects of WWII on those who were victims of it, if they left. It requires finding a lawyer who can compel them to open the records to you. I won't recommend any one lawyer, but in such cases, a lawyer is required to simply get access to the records.