Замените существительные с предлогом "of  существительными в притяжательном падеже:
- the
flat of my mother, the children of my sister Mary, the letter of my friend, the stories of
this writer, the younger daughter of my brother;


-       the
house of his parents, the rights of the women, the children of my
sisters, the car of my grandparents, the room of her brothers.

My mother's flat; my sister Mary's children, my friend's letter; this writer's story; my brother's younger daughter; his parents 'house; the women's rights; my sister's children; my grandparents' car, her brothers' room