Partition of Land and House

My father With first wife had 4 childrens(1 son & 3 daughters). After the death of first wife, he married again(my mother) and had 2 childrens (2 sons). My father had a land of 2.73 acres which he inherited from my grandfather and a house property 60×40 in which he builded 2 houses, 2 shops and a garden. My mother, me & my brother are residing in a house and the son of first wife is residing in the other house and doing business in both the shops. Now the son of first wife is demanding half of the land and half of the house property i.e 1 shop and 1 house. Even my half sisters are asking their rights in the property(of course we r ready to give). The son of first wife is a drunkard and made lot of debts in the name of my father and my mother paid all those debts except one debt for 5L which that creditor filed a case against my mother. Now how should we divide the property? Both land and house ?? Should v divide the house property as per land area or as per shop and house? Please clarify about what share my mother, me and my brother will get.