Land / House among 3 brothers and nephew

Father had put all the 3 brothers name in housing property which is built on a land (its a bunglow). one of the brother was not staying in the property and had died long back in 80s leaving behind wife and 3 kids. later the 3rd name was transferred to wife's name. Even the wife and 3 kids were not staying at this place. All the property tax and other taxes and bills were paid by 2 brothers till now who are currentl staying there. 3rd brothers wife passed away few years back and later these 2 brothers came to know that 3 childrens (of 3rd brother) had added their name in the property without any consent though legally it belongs to them. Now since the house is already existing (and renovated) and there are 2 seperate doors for each brother, these 3 kids (of 3rd brother) have come and telling they want to stay in this place. Giving their share is not an issue. But since the house is already built with 2 doors and 2 seperate electricity meters and both (the brothers) their families are already staying. can you please give us some suggestion 1) Legally they have the rights, but they have not stayed there for more then 20 years and not paid any bills or taxes. how much right is there in that house? 2) can we ask them to build a new big house with 3 seperate doors (with seperate meters) for each of the families? In this 2 brothers with contribution the least in that house? basically 3rd brother's kids will contribute half and rest half will be divided between the existing 2 brothers (families). 3) As the house is already exisitng and built on the land, hardly any space is left for the 3rd house to be built and its road touching property. please suggest is there any other options? Also these 2 doors on the same land are 2 storey (ground plus one). Both the brothers have given one floor on rent. can they claim these 2 floors which is given on rent?