Literature Reference: 恺，乐也。——《说文》；昀，日光也。——《玉篇》 Kai means joy, as recorded in 'Shuowen'; Yun means sunlight, as recorded in 'Yupian'.
恺: Happiness, harmony; triumph.
昀: Sunlight, sunshine. When used in personal names, it often symbolizes brightness and hope.
Meaning: Kai signifies joy and harmony, while Yun represents sunlight, symbolizing brightness and optimism.