A Question about German "genitive" (Genitiv). "The child's father is in Berlin."---"Der Vater des Kindes ist in Berlin." "The child's mother is in Munich."---"Die Mutter des Kindes ist in München." "The children's parents are in Leipzig."---"Die Eltern der Kinder sind in Leipzig." I know the sentences above, and they all use "Genitiv". But how to explain the sentences below? "He is my elder sister's son."---"Er ist der Sohn meine ältere Schwester." "She is my elder brother's daughter."---"Sie ist die Tochter mein älteren Bruder.” Why here is "Nominativ"?