Is a quit claim deed legal and enforcable on property you are an heir to but is still in your parents name?

In 1975 my Grandfather passed away and in 1970 my Grandmother passed away. In 1977 my Mother signed a quit claim deed relinquishing her interest in this property to her 5 brothers. The document was filed with the state of Illinois. The property title is still in my Grandparents name and I am told that I have no right to any interest in this property due to my Mothers quit claim deed. Is this fact true as my cousins insist as all 5 brothers of my Mother have passed away or can I claim interest to this property as a Grandchild to my Grandparents who still have title to this property. Thank You