Hint

• father_of(Father,Child) and mother_of(Mother,Child):
  Fathers are male parent and mothers are female parents.
• grandfather_of(Grandfather,Child) and grandmother_of(Grandmother,Child):
  X is a grandfather of Y if X is a father of Z and Z is a parent of Y. X is a grandmother of Y if X is a mother of Z and Z is a parent of Y.
• sister_of(Sister,Person) and brother_of(Brother,Person):
  X is a sister of Y if X is female and Z is a parent of both X and Y.
• aunt_of(Aunt,Person) and uncle_of(Uncle,Person):
  X is an aunt of Y if X is a sister of Z and Z is a parent of Y.

Solution

Back to the exercise.