dispute

Dear sir, we have a land in dimapur. Which is in my father-in-law name. Actually it was not bought by him. May be in the year 1975 or 1977, the then govt of nagaland has given the land patta to many homeless free of cost. During that my father-in-law was not working for the livelihood of his wife and 6children. But my husband uncle(chachaji) , who was a bechelor has helped my in-laws in food ,clothing and education. Till my husband started to helped the burden of his family, when he was just at class 8. My husband was good in study. He use to do part time job to help his family and also continued his studies, untill he completed his B.sc in mathematic. After that he started teaching in school. From that time he was the only earner in the family with 9 members. With his income he married of 2 elder sisters. His family consist of 3elder sisters , 1elder brother n 1younger brother . My husband is the fifth child. My mother-in-law died in 2008 due to lung cancer. Where all Medical expenses was bear by my husband and again the same year his uncle died due to high pressur. At that none of his brother helped him as both of them were nt earning. So my husband was in debt. Even during that his younger brother married his girlfriend, who was jobless. So all the burden was faced by my husband. In2009 we to got married in a temple. Me to was a teacher , after my marriage. I helped him in paying of his debt. But today to my surprise some customer to buy our property without our knowledge. My father-in-law and 2 brother-in-laws are trying to sell the property which is worth of around 16 lakhs. Please help us, how to deal with this Problem.