It was said his father was very ill and his doctor had said his father could pass away in a few months.

pass 的基本意思是"通过、经过"，在这里与 away 搭配使用。 away 的意思是"离开、远离"，在这里与 pass 组成短语。 pass away 是一个委婉语，意思是"去世、逝世"，用来代替 die 这个直接的表达方式。