Ordinary Children (1978)

Four years ago, Igor, Olya's father, fell in love with another woman, Tatyana, and left his wife. Tatyana has a son, Dima, whom Igor is adopting. And one day Igor can not meet Olya, and sends Dima instead. Children get acquainted. There is a paradox. Olya hates Dima and his mother, he is friendly. Children have to cross the line of love and hate.