Real estate ownership??

My mother-in-law recently ped away. She didn't have a Will for her three children for her estate. Her house that she left is the point in question. About 3 years ago she had gotten into some financial bind and had asked her son and daughter-in-law to co-sign the house. My mother-in-laws' intention is to leave this home for her 3 children to share financially. Now my brother-in-law who is living in the property , consisting of a main house with 2BR + 1 duplex located in the compound with 1BR each, was basically renting 1 of the duplex with his family. He payed very minimally for the mortgage,which was being paid mostly by my mother-in-law. My mother-in-law her son and daughter-in-law lived approximately 3 years in this setting. He also payed some of the utilities. Considering the average amt. being payed for a 1 BR in L.A., he was living a life under his moms home with his own family. What can the other 2 siblings do legally to get some form of ownership to this home?