%age ownership to mom brother and sister on property bought by my father and me.

My father had asked me to help take a home loan in 2008 to help buy a house together. I took the home loan for about 1/3rd value of what was asked by the builders. The property is in the name of my father and me. My father passed away many years back. my younger brother is claiming to be 50% ownership to this. he stays in one floor and my mother stay in another floor. I have beein staying in another city but i am planning to come back to the city where i have this property since my kids are growing up. he says since he paid out some money (from the outstanding loan amount to me, he paid this after over 6 years of me paying every single EMI). i had already deposited money in the bank for the emi for the next two years or so. so i did not really need his money but my mother asked him to pay this since he had a nil contribution at home. It was never said that this was for a share in the property. also he paid this after 6 to 7 years of me paying the emis. He is also threatening me that he will put a cheating case on me if I dont agree to changing this via gift deed. please advice. my father had 3 children including me 2 sons one daughter and one wife, my mom. is his claim even valid? Also what should be the sharing %age on the property now as per indian law.