Ancestral property issue

It is a legal WILL. When each transfer occurred by WILL, it cannot be ancestral property. 

once if a property is transferred through will to another person it loses the character of ancestral property

As it is ancestral property C can make will but upto the extent of his share only.  You have not stated that whether C has any other siblings i.e. brothers and sisters and you have not stated your religion.  

Shed out your apprehensions.  It is not ancestral property because the property is in the hands of your grandfather inherited by him from his mother  through a Will. This was a woman's property which was transferred by her to the person of her choice, therefore no question of ancestral property arises.  Even if it is considered to inherited from his father by your grandfather and assuming the property to be self acquired property of your grandfather's father, th property came into his hands by a Will, then your grandfather becomes an absolute owner of the property over which he has got full rights to dispose it in any manner he desires so and to anyone of his choice.  Nobody can compel or force him part with the same for any reason. 

It transpires from the given facts that originally the subject property was under the absolute ownership of Grand father's mother i.e., 'B'  but after her death said property was automatically devolved upon her husband i.e., the  Great Grandfather of the author deascribed as 'A'. After the death of 'A' i.e., great grand father the property devoved upon the grand father i.e.,'C', but the author is silent about the facts how the property was devolved upon 'C'. Is he the only legal heir of 'A', or 'C'  has any other brother or sister (? ), or 'C' became the owner of the property by virtue of a Will or Codicile of 'A'?  In absence of such facts legal opinion is not possible.