For instance, his biological father, Zhang Dacai.
To bring forth life without nurturing can be remedied, but to nurture without giving birth is an inexhaustible debt.
"Su Peng, do you think I'm being heartless?" Dealing with her own biological grandmother without showing kindness, others would definitely say he was unfilial.
"Not at all," Su Peng nodded. "Actually, my situation is pretty similar. My real dad gave birth to me but did not fulfill his responsibilities, and I don't have any affection for him."
"I've heard you talk about it before," Wu Wenli bowed her head. "It's good that you can understand me; I'm just worried that my aunt might misunderstand me."
If it were someone else, they would definitely advise to let bygones be bygones, after all, she is his biological grandmother, and family ties are inherent.
Some feelings can't be truly understood unless you have experienced them yourself.