他是我的太阳却是别人的光
[tā shì wŏ de tài yáng què shì bié rén de guāng]
It implies the person is indispensable yet unreciprocated love - the person cherished like the sun, the center, but their light belongs to another person rather than illuminating the user’s life as much as they wish. A bittersweet and somewhat sorrowful sentiment, possibly about longing, envy, or an unrequited emotion.