what to do if someone deny aftr power of attorney

my father is ill, one of his brother who was showing too much affection towards him asked him that, give me power of attorney so that i will sell your property, marriage ur daughter, give money to ur sons, make goldnecklace to ur wife etc, and once we let our dad to give him power of attorney, he started avoiding to give a agreement bond regarding it, also he had created a false SR pawti which says my father has writely sold him his farm in 57 lakh which he had paid 8 lakh, but interesting fact is, my fathr n that uncle etc got this farm property equally from their late brother, and after this property get registrd for my dad name, he get paralysed in 3 4 mnths so how come he will give it to his bro if he himself can sell it that time, also now that bro harassing me my mothr sistr brotthers tht u all are not carring ur fathr thts y i will not going to sell it n giv u money,s, what we can do now? with father and without fath, suggest both way