Theirs had been an increasingly attenuated relationship.是什么意思？

Theirs had been an increasingly attenuated relationship.

他们的关系日益冷淡。

theirs

pron. 他们的，他的或她的；

例句
He would leave the trailer unlocked. If there was something inside someone wanted, it would be theirs for the taking...
他不会给那个活动房屋上锁。里面要是有什么别人想要的东西，他们可以尽管拿。

had

v. 有（ have的过去式和过去分词 ），（亲属关系中）接受，拿，买到；

例句
He claimed that his parents had abandoned him...
他声称父母遗弃了他。

been

v. 用来表示某人或某物即主语本身，用来表示某人或某物属于某一群体或有某种性质（ be的过去分词 ），在，存在，不受干扰，去过了，be的过去分词；

例句
Have you been able to have any kind of contact?...
你联系上了吗？

an

art. 一（在元音字母前代替不定代词a），一任一某一，一个；

例句
He started eating an apple...
他开始吃苹果。

increasingly

adv. 越来越多地，日益，格外，越来越…，愈；

例句
Theirs had been an increasingly attenuated relationship.
他们的关系日益冷淡。

attenuated

v. （使）变细( attenuate的过去式和过去分词 )，（使）变薄，（使）变小，减弱；

例句
Theirs had been an increasingly attenuated relationship.
他们的关系日益冷淡。

relationship

n. 关系，联系，浪漫关系，血缘关系；

例句
Our relationship made me feel more alive...
我们的关系使我感到更有活力。