英语关于同位语从句Do you know the truth that where there is life ther

英语关于同位语从句
Do you know the truth that where there is life there is hope ?
～～～～～
请问作为同位语从句这里为啥这里加了THAT还加WHERe

EG, have no idea when he will be back．我不知道他什么时候回来.
He must answer the question whether he agrees to if or not.
他必须回答他是否同意这样一个问题.
此处就没用THAT而单个连词

Do you know the truth that where there is life there is hope
这个句子是从句中套有从句了.同位语从句中又含有一个地点状语从句.如果这样改写这个句子你就看的清楚了.
Do you know the truth that there is hope where there is life