My step brother was not named in my mothers will, he was named in my fathers before his passing. can he contest the will of my mother

So both of my parents have passed. My step brother was named in my fathers will at one time, after my father passed my mother had her will changed to exclude the step children and for it only to go to my biological sister and I. My mother has since passed from cancer and we are afraid that my step brother is going to contest the will. My mother did leave an addendum that she didn't sign prior to her passing leaving him some money but not nearly what he is now asking for. After her passing we did allow him and the other step children come to their home and take many expensive items without any issues. Essentially we told them take whatever they wanted because we didn't want them to feel left out, which they did take many items. Does he have any legal right to contest the will. Our relationship with him was for the most part decent and his tone has only recently changed since her passing. He does live out of state, We are in Pa and he is in CA.