Sympathy Death Of Mother Do I Send My Father In Law A Sympathy Card On His Mothers Death.What Is The Etiquette.?

Do I send my Father in Law a sympathy card on his Mothers Death.What is the etiquette.? - sympathy death of mother

As my mother and my grandmother for the children of Great Grandmother. Not sure if the family because they are immediate. I do not want to offend anyway.