Can my sister-in-law claim the property

My husband's grand father owned a lot of property. My husband's father sold off the ancestral property and bought a house. My husband's father died in 1998 without writing a will. In the year 2006, my husband was pressurize from my sister-in-law and mother-in-law to add all three sisters, mother's name to the property. My husband on good faith himself did that. Now they want t sell the house and divide the money in five equal shares. Since 1998, my husband has been looking after the house, paying all property tax, nazool, and investing in repairs and maintenance. He has also been taking care of his mother and fulfilling all of his soical, financial responbilities towards her as she has no income of her own. They have one tenant who has not been paying rent since 2015 and not vacating the house. Their son is selected for civil judge exam so they have become even more aggresive. My husband is fauji who because of this trouble keeps going to home town to resolve the issues. I believe , if father dies before 2005 without writing a will, and property is bought by selling ancestral property. Then sisters have no rights Secondly, rights and responsibilities go hand in hand. His mother has been staying with us. in such a situation i want the legal advise.