Land dispute

Sir, my father has written a veelunama of 613 sq yard plot which is having house with built up area of 256-26 sq yard to me and my brother which was registered. My father has written clearly that the property will be enjoyed by us after him only. The RCC house was 1/4th in my share and 3/4th by my brother share. After my father if i want to sell the property or built a house in my share, can i directly dismantle the 1/4th building which was in my share or any legal problems were arise. My father is still alive if any problem he can change the veelunama. Can you please suggest the suitable solutions for this. Thanks srikanth kvs