There is one bad theme that ran throughout the LOST story lines.
The affect of parents' treatment of their child had a dramatic effect on how that character was as an adult.
Jack's father never gave him the praise or encouragement Jack needed in order to complete his socialization process. As a result, Jack was not capable of having strong relationships with other people. His displeasure for his father's treatment of him was transferred onto other people he cared about when he was an adult.
Sayid was pushed into being a man as a child. He had to kill the chicken when his older brother could not do it. Sayid was trapped into following authoritative directions. He lost his own free will to serve his superiors (his father, his army commander). As a result, he did things he did not want to do (torture people) and to give up any dreams he had for his future (Nadia).
On the other hand, Hurley's dad's abandonment of him caused Hurley to develop a severe introversion with other people. Even when he had the courage to socialize, it was with the fear of rejection and abandonment. When the store clerk he liked ditched him for his best friend, Hurley's only escape was into his own dream world, a safe place where he could not get hurt.
Sawyer's mother and father ruined his life. His mother was conned out of the family savings, and his father went nuts by a murder-suicide with his wife instead of trying to rebuild his family trust and savings. That led Sawyer to a life of crime and revenge that de-humanized him to become the person he hated the most in the world, the con man Cooper.
Kate's parents divorced when she was a baby. Her mother fooled her into believing her second husband was her father. This deception led Kate not to trust men but to use them as puppets in her own bizarre rebellion. Kate's situation led her to a life of refusing to take responsibility for her actions, and to run away from her problems like her parents did when they divorced.
Jin and Sun were opposites tied together by their hatred for their family class status. Jin fled his poor fishing village life to vow that he would become a rich man. Sun rebelled against her strict, patronizing industrialist-criminal father. She would never get the status or position in the family business because of her gender. She took satisfaction that her father could not stand her taking a poor man like Jin as her lover. But she mistook Jin's desire for wealth over true love when he turned into her father's lackey. There relationship was based more on fighting back against their parentage than true feelings for others. In a way, there childish selfishness against being like their parents was their demise. No one can believe that one parent would orphan their child by drowning in a submarine; death was better than being a single parent?
Locke's traumatic childhood was the deepest cut of all. He could not find the family that he was searching for. He was blinded by the thought of a perfect, suburban picket fence reunion with his real parents. But their loathsome self-absorbed personalities destroyed Locke for a second time. Locke was so beaten down by his upbringing that he could not see the one woman who truly cared for him. He was so bent on his past he could not live in the present. He lost his family and the one woman who loved him. He created his own destiny of being a poor, miserable, bitter man because of his parents abandonment of him as a baby.