My mother IS my father's WIFE
My father IS my mother's HUSBAND.
My mother and my father are my PARENTS.
Mr. Smith HAS got two CHILDREN a son and a daughter.
My mother's sister IS my AUNT.
My father's brother IS my UNCLE
His brother HAS got two sons.
They ARE my father's NEPHEWS.
My father has (ничего не надо ставить) a sister, too.
His sister HAS got one (тоже ничего не надо ставить) daughter.
So my father HAS got a NIECE too.