I want to get an inheritance I was cheated out of

I'm sorry to hear that ! In order to challenge this will, you have to prove that there was lack of testamentary capacity, or that the person was subject to undue influence.  You will need to speak to his doctors to determine his mental status at the time the will was drafted, and speak to the attorney that drafted the will.  I might be able to help you on this matter if you would like.  call my office.