désolé ma chère soeur
soeur is "sister" in French
To write "my sister" in French, you would say "ma soeur."
Désolé votre sœur
"Pardon" or "Je suis desolé"
Dear Uncle bob, I am sorry to inform you of the death of your sister. Kind regards, John Smith
first of all I'm am so sorry if your sister has died! write the good and funny things about her and say how much you will miss her. if you think you might cry then keep it short.
"Ma soeur fait ses études au collège."
their sister -> leur sœur
ma belle sœur et nièce (only my sister is beautiful) mes belles sœur et nièce (they are both beautiful) note that "belle-sœur" in French sounds exactly the same, and means sister-in-law. A French speaker hearing this will certainly think of your sister in law.
"Sister" in French is "sœur."
"Sister" in French is "soeur."
A sister is "une soeur" in French. The plural is "des soeurs".