I am so sorry for your loss and for the problems that have resulted.  I think that you should speak with an attorney in your area on the matter as soon as you possibly can.  I do think that you may have the basis for a challenge to the changes in the Will but realize that it could get costly and is so fact specific that no one in this type of forum can let you know for sure.  If your Grandfather's Will was changed close in time to his diagnosis of Alzheimer's it will be your position that he was not of sound mind to execute the new Will.  Also, I am curious how your Uncle was appointed as Power of Attorney as well if your Grandfather was diagnosed with Alzheimer's AND how your cousin could possibly handling the estate, since there is no doubt that your Grandfather could not execute a new POA in June of 2009.  Your cousin's status has no effect on the status but could on the handling of the estate.  Good luck to you.