Reason: First, both his sisters have Jia characters, and he also means to be close to his sister. Second, Jia has soil (scholars are wise soil), and the combination of the five elements is beneficial to his life. Thirdly, this word is auspicious and harmonious in phonology.
People upstairs don't know Chinese characters, and they are talking nonsense.
Cheng Zi is very good! And it contains double soil, good luck.