The earthquake made the surviving lovers sympathize with each other to overcome their difficulties. Is the idiom used correctly?

It is more appropriate to change "let" to "make".

When both sides are in a humble situation, help each other

Pinyin xiāng rú yǐ mò

Explanation: wet; Bubble: spit. When the spring dried up, two fish spit and wet each other. Metaphor in difficult situations, help each other with meager strength, just to save a life.