一生一世一双人相思相望不相亲
[yī shēng yī shì yī shuāng rén xiāng sī xiāng wàng bù xiāng qīn]
Derived from classical Chinese poetry, meaning 'one lifetime, one spouse - longing for each other but unable to be together'. It carries a deep, sad love connotation of longing and unrequited love.