Blood Relations

Step 1: Identify the four generations.
Let’s denote the youngest daughter as Generation 1 (age 6). Her elder sibling (also Generation 1) would be years old (due to a 3-year gap). Step 2: Find the father’s age (Generation 2).
According to the problem, a father is 30 years older than his eldest child. So, the father is: Step 3: Find the mother’s age.
She is 3 years younger than her husband: Step 4: Find the grandfather’s age (Generation 3).
Father’s father is 30 years older than him: Step 5: Find the grandmother’s age.
She is 3 years younger than her husband: Step 6: Compute the difference between the youngest daughter (6) and the grandmother (66):

A is the mother of D, so D is A's child. B is A's sister, so B and A are daughters of C, as C is the father of B. Therefore, C is the father of A as well. Since A is D's mother and C is A's father, D is the grandchild of C. Thus, the correct answer is: