Uncle is threatening to sell the property what can be done ?

We are living in a bungalow which was constructed 21 years ago . All the 4 Brothers including my father paid for land and construction of Bungalow but it was decided that the property will be registered on the name of 2 Uncles as they were Government employees at that time for easily accessing loan My Dad believed on them and agreed to there terms . Since 20 Years we are living in Property and now my uncle is threating to sell the Property including our house .Please help. (Bungalow is divided into four 2bhk flats for 4 brothers)