# 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`

.