Is there any way he can force the sale of this building and return home to England?

My neighbor has asked for advice. I don't know what to tell him. In the 1970s, he and his wife purchased a duplex. At his wife's request, the wife's sister was added to the deed, despite the fact that she contributed nothing to the down payment. Each person owned one third of the duplex as tenants-in-common. He and his wife paid 2/3 of the mortgage and his sister-in-law paid 1/3 until the house was paid off. He and his wife lived in the upper unit and the sister-in-law lived in the lower unit. Ten years ago, the wife died. They had a trust, and he inherited his wife's share. He remained in the upper unit and the sister-in-law remained in the lower unit. He now owned two thirds of the building and continued to pay 2/3 of the maintenance. He is now in his mid- eighties. He has difficulty going up and down the stairs, which is a hardship at his age. He wants to sell the property, take his two-thirds of the sale, and return home to England to live with his daughter before he passes. Needless to say, the sister-in-law refuses to consider selling. She does not want to leave and her 1/3 share would not allow her to purchase anything in the city. Also, the sister-in-law does not have spouse or children but does rent out one of her bedrooms. Is Tom stuck here?