his sister / her sister
Alors, lui et sa soeur, Franci, sont arrivés.
Then he and his sister, Franci, arrived.
— Carandiru (2003)
Parce que c'était la nuit où Kelly, a descendu son mari et sa soeur.
Because it was the night Kelly shot her husband and sister.
— Chicago (2002)
Peut-être même plus dur que de tuer sa soeur.
Perhaps even harder than killing one's sister.
— Avengers : Infinity War (2018)
His sister.