Contesting a will

My uncle lived in NM, we the 5 of his niece and nephews were to inhearit his estate. Approximately 5 years ago he was at beginning stages of alhemizers, had a girlfriend, bad influence), his brother and aunt and my mom, (sister inlaw), had to sell his house and move him into assisted living and made sure it was a place the girlfriend could not go with him. He passed away 5 days ago and the will was changed from all of us getting it to leaving everything to two charities he was not involved or believe in. None of us had a falling nor a change in our relationships. We believed he was not right of mind and influenced to alter the will. What can I do to challenge it. My aunt and uncle are the executors of the will but are not contesting it. What are my rights and steps to take.