Property issue

Hi, My grandmother transfered the house to by dad he is the elder son in the family, but there is no record any where he only had the ration card stating the property is in his name. but in course of time my uncle who is younger to my dad had some financial issue and he wanted to take loan for his sons education though he didnt have any owned property so he requested my father to tarnsfer the house in his name for some time till his sond education is done. on good deeds my father did that and this transfer was on plain paper with one witness and this house is in a chawl where no agreement is done . so now after 25 yrs my fathers other siblings is asking my father to sell the house and give the share when my father said the same to my uncle he is not ready to give the property he is not buying it nor he is giving in writing that in any point of time if he sells the house he will give the share. the other thing he has given that house on rent and his son is well settled now but still he denies to give back the property . what sought of case can be filed and how do we go about it and recently we came to knw that the billchange has been done to my uncles name but without my fathers knowledge and also we dont have any proof that the particular house was in my fathers name . and also wanted to knw does all the children have equal share in the property do any paper document is needed for the same or it is for all by default unless there is any wil.