If we were to assume that Cheng Ziang is the son of Yalunte and Princess Lin, it's clear that he doesn't know about his parents' true identity, given the nature of the questions he's asked. As a result, the headquarters have likely withheld this information from him.
Judging solely on Cheng Ziang's appearance, it can be somewhat perplexing. While it's been noted that he doesn't resemble King Gudelv, he only bears a passing resemblance to Princess Lin too. Shariya even spotted traits that the Shani people from the headquarters possess.
If Cheng Ziang were genuinely a descendent of Yalunte and Princess Lin, he really doesn't resemble either of his parents.
