1. Kimberly exudes aristocratic atmosphere, which makes Xu Er admire him very much.
2. Kimberly is the yearning and hope of the civilian class represented by Xu Er, and expresses his yearning for a better life through taking care of him.
3. Xu Er may yearn for the aristocratic life, and he can approach and understand this lifestyle through his kindness to Kimberly, thus satisfying his yearning for the upper class.
The above are only possible reasons inferred from public information, and the specific reasons may require more background information and in-depth understanding.