Can a inlegal son claims on his inlegal father prorerty

Sir, There are 4 son ( jawahar, shobhi, heera and babu ) and 1daughter of my grandfather . His daughter is married now. Now Babu,s family settled in agra and heera ,s family settled in lucknow. And jawahar,s family and mr.shobhi lived together on my grandfather,s property and take care the farms . After death of my grandfather total property and farms devided in four parts . After devidetion mr. Shobhi lived with mr.jawahar,s family... Mr.jawahar have 3 son ( jitendra, amit, satendra ). mr. Shobhi was unmerried ..and he dont make any will in his life. Now after death of jawahar and shobhi. When my father babu says to jawahar,s wife devided property of mr. Shobhi in 3 parts .then jawahar,s wife says that the boy amit is mr. Shobhi,s son by inlegal affairs with her. property will give only to amit . And there is no share of anyother. Sir plz tell me 1 -- this type of relationof ( jawaher,s wife and shobhi ) is leagal or not...... 2 -- amit is legaly able for mr. Shobhi,s property or not..... 3 - what is indian law......in this condition for me....... ..............sir plz tell me....