Legality of change in Will

I am not admitted in Texas.  I am sorry for your loss.

A party who has "Testamentary Capacity" can change their will at any time.  There are, however, two red flags here:  "96 year old man" and "caretaker".  There have been cases where caretakers have "unduly influenced" the elderly people they care for to execute new wills leaving their estates to them and cutting off relatives, especially if the elderly were not of "sound mind".   Each case is fact specific.

You should seek legal help from an attorney n your area on this.  It may be a case of undue influence and you will need to bring a proceeding challenging the Will.  It is a costly matter and your success will rest on many little pieces to a puzzle only an attorney can help you put together.  You can start looking here at attorneypages.com.  Good luck.