Hello. I would not let this go just yet and try to get the DOS to reinstate the visa registrations due to government error. It would be a severe loss if you had to restart the process since the siblings category is over 12 years behind. Regards.
You can try to reinstate but it is not likely. The notices as is the normal practice were sent to the address(es) of your brother and sister abroad. The notices from the consulate are not sent to the petitioner's US address.
If you are unable to reinstate the old petition you would lose the priority date so you take action to maintain the existing petition. DOS can only terminate a petition under limited circumstances and we don't know all the facts in detail. Consult with an immigration attorney experienced in consular issues who can review the case in detail and recommend an appropriate course of action.
While this answer is provided by a Florida Bar Certified Expert in Immigration and Nationality Law, it is for general information purposes only and an attorney/client relationship is neither intended nor created. You should seek out qualified counsel to review your case and provide you with advice specific to your situation. Review Mr. Devore's Avvo Profile for more information about his expertise in immigration law and how to contact him to discuss your case.