“Apologize to your mother. And stop making a scene!”
—Quan, in Book 5: Lodestar
Quan is described to have jet-black hair and silvery eyes, like his children, but no silver-tipped bangs.
He puts a huge emphasis on appearances. He does not want his reputation to be tarnished by his children, as they are twins, and so he tries to hide the truth from the public, is afraid of making a scene in public and feels ashamed of Tam when he draws unwanted attention. He also shows disapproval of Tam's silver bangs.
He firmly believes in children respecting their parents but seems to think children have to respect them no matter what, kind of like brainwashing.
Quan doesn't like the fact that Tam is a twin and is harsh and disrespectful to him which makes him rude back to him.