Elderly (86), sick (end stage renal disease) doting Grandmother has told her deceased daughter's 3 children that they would be given equal shares of their mother's inheritance upon the grandmother's death. There were 3 siblings, brother and 2 sisters. Youngest sister died in 2002. 34 days before her death, the Grandmother signs a quit claim deed giving both homes to the surviving sister and brother. Keep in mind that she has NEVER given any indication that her deceased daughter's children were to be denied their mother's 1/3 of the estate.
The grandmother was on prescribed narcotic pain medication (hydrocodone) at the time she "signed" the deed. No proof that she ACTUALLY signed the document has been forthcoming.

This does not pass the "smell" test!
Is there anything that can be done?

...No proof that she ACTUALLY signed the document has been forthcoming. ...

Her signature, notarization, and (as required in some states) signatures of witnesses are proof. Not irrebuttable proof, but proof.

If you suspect she didn't have the mental capacity to sign the deed, ask yourself who would inherit the property if the deed is thrown out. Depending on what state you are in, the grandchildren by the daughter who failed to survive grandmother may inherit a 1/3 share, but it's not a given.

Of course they can sign, other family members can challenge her state of mind if they wish.
But she is allowed to sell or give away to anyone she wants to.

... The grandmother was on prescribed narcotic pain medication (hydrocodone) at the time she "signed" the deed. ...

I'm not an M.D. but that, in of itself, doesn't seem enough to make her mentally incapable of making a rational decision.

"Common side effects include dizziness, itching, lightheadedness, nausea, sweating, drowsiness, constipation, vomiting, and euphoria. Vomiting in some patients is so severe that hospitalization is required, although this can be due to alcohol consumption before taking the medication.[citation needed] Some less common side effects are allergic reaction, blood disorders, changes in mood, racing heartbeat, mental fogginess, anxiety, lethargy, difficulty urinating, spasm of the ureter, irregular or depressed respiration, and rash." http://en.wikipedia.org/wiki/Hydrocodone

First problem I see is here:


Grandmother has told her deceased daughter's 3 children that they would be given equal shares of their mother's inheritance upon the grandmother's death

If one of the this woman's children died, then whatever inheritance she left should have been given out when she died. So if it wasn't then there is no inheritance. If the mother left something in trust to her children, then they are entitled to that only.

There is nothing wrong in the grandmother signing a deed. The key is whether she was of sound mind and knew what she was doing. Her doctor or caregivers would be able to testify to that or lack of it. So if you feel she was incompetent, then you challenge the transfer in court.

But, as AK pointed out, if the deed is overturned,the estate would be distributed according to the laws of inheritance where she lived (ANY question on law needs to include your general locale as laws vary by area.). Those laws could disinherit the grandchildren as well.