Even then, Xu Zeng wasn't worthy enough to be married out with some sort of dignity. In the end, they still chose to sell him to a brothel.
His stepmother was cruel, he'd always known. His father wasn't actually his father, this he'd also known before his "dad" died. There was no love between them, but Xu Zeng had no one else.
His only kin was at that time, somewhere in the void, his life and death unknown. His "dad" had passed away during childbirth. Xu Zeng was tolerated by many in Sun Village, but he was never free enough to interact with them.
No one went out of their way to make his life any easier, he was a stranger after all, not one of their own. He wasn't worthy of that much attention.