Because in Xizhimen Beijing Zoo, following the birth order of parents, the panda "Meng Lan" is the only child in its growth period. The giant panda "Meng Lan", also known as "Mo Yao II, Meng Zai, Pang Wa Er and Meng San", is called "Three Princes of Xizhimen" because both parents are the third and only children of that session, and now lives with their mother, brothers and sisters in Beijing Zoo in Xizhimen.