Property issues of my mother.

1. My Grand father & grand mother making a Will Joint together by joint (on 1976 in Tamil Nadu - Chennai) - A B & C (portion) 2. They have four childrens ( 1. Daughter 2.Son 3.Daughter & 4. Son) . 3. Father & Mother did the marriage for the 1st Daughter - so for the marriage cost they not giving any property share to her. 4. 2nd Son - A (portion) & 4th Son - B (portion) marriage were done by them saying by Will, 3rd Sister were spinster of her life and died on 1986. 5. Grand father died on 1980 but Grand mother living upto 2005. 6. Sudden death of 3rd Daughter on 1986 - a portion of (part - C ). 7. Grand mother taking that portion as a owner of the part - C and cancel all the Will which was written on 1976 and making a settlement to her 1st Daughter 1986 (becoz she was a widow and there no share was given to her.) 8. 1st Daughter making a settlement gift deed to their 2 Sons & 2 Daughters on 2002. 9. The 2nd Son & 4th Son were sold their property on 1998 or 2000 & settle their life well. 10 And 2nd & 4th sons were coming for the share on Part - C in 2016 - and saying as per christian law (Protestant). 11. Now my question was they have a rights to claims on portion - C, how it will be... or ?