Heart of Stone (2007)

Original title: หัวใจศิลา

Tor is the illegitimate child of a millionaire and a poor woman. His mother is the "mia noi" or lesser wife and Tor is the millionaire's youngest son. Tor's stepmother, who is the first wife also has a son, named Sawit, or Ae, as people call him. Tor and his mother are treated very harshly by his stepmother and brother. Eventually, his mother dies of pain from abuse while he is still a kid. After his mother's death, he befriends a girl next door named Mintha, who is also a stepchild. Tor and Min have many things in common and it brings them close together. One day, Ae and Mintha's half sister, Kwan bullies Tor to the point he fights them back.