My grandmother and I recently paid the delinquent taxes on property that was left to my grandfather and his siblings. The only living child is his sister who is the one that told us the property was going to be auctioned off if no one in the family came up with the delinquent tax money. She said that she would sign over her rights to the property to the person who paid the delinquent taxes, but now it's a big mess because one of her deceased siblings son wants part in the land. Is there any way we can have a Real Estate Attorney due something like post a newspaper add for family members to come forth and claim the land and if they don't in thirty days no one speaks up the land could become ours free and clear of anymore hassles. Thanks for your response in advance.

Depending on the state and depending on the wording of the will that left the property to the grandfather and his siblings. It could have left it so that the children of deceased heirs will have a legal right to inherit part of the property. But there is a way it goes only to the living members.

This should have been settledin probate thought the will, or though probate without the will.
You most certain need to hire an attorney, he needs to look over the will, and probate or lack of probate in transferring the home to the courrent owners.

And no merely posting is not what needs to be done most likely, but there may need to be a posting of notification of a hearing where the legal status of the property is determined, and a new deed issued to the legal heir or heirs of the property.

It is very likely you have merely given them all a gift in the amount of the tax lien. You would have been a lot better off, actually waiting and bidding on the property at the tax sell most likely.