Does my stepdad have any grounds to contest anything in my mom’s will in regards to my brothers company?

My brother passed away a few years ago. My mother was awarded his company as per his will. The estate still hasn’t been fully settled due to an audit not being completed and back taxes not fully paid. My mother’s health is now in serious decline. She has told me that she is leaving my brothers company to me. She has stated that she is leaving him the vehicles she inherited from my brother’s estate. These vehicles have been titled in his name. She also is leaving him the home that they owned as husband and wife. My main concern is in regards to the company. Does he have any entitlement to any part of it?