Appoint guardian & property

My Name is Jamsheed, My Family Religion is Islam. My Place at Malappuram district, at Kerala. My father, aged 62 and my mother, aged 47 divorced, when I was 7 Years old. Because of my father have mental Illness and lack of care to my mother. Sometime he go to outside and come back after 4 or 5 days after. My Mother did not know about his illness before their marriage. When I was in 1 years old mother leave from the father's family home. My Father have 3 brothers and one sister now. My Grand father died before My Father's Marriage. My father live in family home with brothers. When I was in 12th class (2003) I fist see to my father in his home. and after I go to my father alternatively. and give some money to my father. My father is a good farmer. he working more in farm, and the farm items (Banana, bitter gourd, etc)give to my small brother's family. Later, 2009 I went to Gulf for my job for six years. Then come in 2016. I stop my expatriate. Then I saw the father. When 2003 the partition suite take my Grand mother's property. I asked my father as guardian. The small. My father got 40 cent and hose with small brother joint and 19 cent other properties. In 2012, They take document separation each 20 cent, the house was destroyed, the fathers land have no walking way and The small brother's son made a new house in my fathers land without knowledge of me. They take exploitation of My Fathers Mental Illness (He have Medical Certificate write it, Mental Impairment, 45 %, schizophrenia, Permanent Nature). I am only one son of my father. with knowledge of document I asking their fault. The Small brothers family shouted me. Wrong words use. they refuse me. They told me you did not my father's son and do not give you your father and property. I ask my father can you come with me, he tell me he did not come from his place. My father do not know what they doing and talking. My Queries is, 1. How can get me my father's guardian? 2. How can adopted by law? 3. How to cancel 2012 document separation? 4. How to protect my father and his property?