恩,是定语从句的省略.
Children of the Great Depression前省略who are.
Children of the Great Depression提前表“强调”,这句话也可以说成：
Ish and Arlene,children of the Great Depression,were known for their habit of saving.
意思是：大萧条时代出生的孩子爱西和阿林,他们以勤俭节约而知名.