How to understand the sentence that the father is heartless and the son is unfilial?

Literally means that the father is not kind and the children are not filial. More broadly, if parents don't love their children, then children won't have feelings for their parents.

I quite agree with this sentence. Love should be mutual. The affection between parents, children and even any relatives all stems from the blood relationship that blood is thicker than water, but the degree of this affection depends on the acquired interaction.

Man is an emotional animal and will not act on instinct. Many parents believe that no matter how they treat their children, they will be close to them. Therefore, they will scold and sneer at their children, and even regard them as buckets to vent. It is hard for a child who has lived in this family for a long time to imagine that he will not have a grudge against his parents, although it may be a secret resentment. On Douban, there is a group whose parents are evil. At first glance, the members of this group told their dissatisfaction with their parents. However, if parents, who are supposed to be the children's most trusted protectors, intentionally or unintentionally hurt their children, what a great impact this will have on their lives. The child may not be able to master topics such as trust, love and intimacy in the future.

I have a female classmate who is beautiful and smart, but she is not popular with her mother, perhaps because she was injured in dystocia at birth, or because she is a second child, so she is naturally ignored. She said that she only remembers the first time her mother touched her since she was a child, and she still remembers the details of the only scene. Mother verbally humiliated her from time to time, and she didn't even know the reason for being humiliated. Now, she has worked as an adult. She will buy gifts for her mother, give her pocket money, and talk and laugh. Outsiders seem to be a kind and filial mother. However, deep down, she knows that the relationship with her mother is always difficult to be intimate, and that kind of love is more responsibility than trust.

That's it. Any relationship needs to be maintained. When a person comes into this world, from a baby to a teenager, he is vulnerable and helpless. If he can't feel the love of his parents, how can he treat this cold and cruel world warmly? Such a child, who has no resentment towards his parents, is good. How can he expect his parents to return love?