I was the administrator father's estate. All was done legally but later found an unpaid debt to a mortgage company. Liable?

THIS ANSWER IS NOT INTENDED TO GIVE YOU SPECIFIC LEGAL ADVICE With regard to liability, the distributees of your father's estate are likely liable for their pro-rata share. Assuming you are a distributee, then yes, you are likely liable, but not as the administrator, rather, as a beneficiary. See O.C.G.A. section 53-7-43 (1997). This, of course, assumes you had no notice of the debt and otherwise did not breach your fiduciary duty to them. If you made distributions with an awareness of the debt, you might have some personal liability in your capacity as administrator. Depending upon the mortgage terms, your brother and your father's estate are probably both jointly and severally liable. If your brother has not defaulted and there was no other default, the mortgage company may not be able to pursue your father's estate on the obligation. I recommend reading the mortgage agreement/security instrument to find out if a default has occurred and assess whether or not any current liability exists. The statute of limitations on the liability is probably at least six years. Because of your father's death, the statute of limitations which applies was probably tolled (i.e., extended) from the period of your father's death to the appointment of you as the administrator and possibly some additional time. Thus, the statute of limitations may be more like 7 years. Other circumstances might extend the statute even beyond this.

Since you published the debtor-creditor notice, you are probalby insulated if they did not make a claim. If you filed for discharge, and were discharged, you are protected. If you did not obtain a discharge, you will still have to deal with the issues raised by the creditor. You should file for discharge and list the new creditor as a known unpaid creditor and let the court tell the creditor that it is out of luck.