“Who am I?” This question is of central importance for adult replacement children, though many may be unconscious of their condition. Others do question themselves: “might it be that I am someone else?” Identification with another person precludes the development of one’s true identity and can lead to serious mental health problems and physical harm. Adult replacement children can suffer from depression and other symptoms, with the underlying cause often overlooked, especially when the replacement was kept a family secret. If assigned the role of a deceased, the individual is not seen for who she or he is and an “as if” personality or “false self” undermines self-esteem and leads to self-alienation. Some suffer from a feeling of “void” or extreme loneliness, others fear the abyss of non-being. Others may wonder: “Why am I?” particularly when told they would not exist if it were not for the disappearance of another human being. In other cases, so-called “saviour children” are conceived to provide vital compatible transplants for an ailing sibling, receiving the projection of a hero child. This chapter also discusses implications of a replacement child being of the same or other gender as that of the lost child, and the importance of the first name for identity development. A famous case is Vincent van Gogh who replaced his brother Vincent, who had been born on the same day but one year earlier. When so-called “deposit representations” have been folded into the self-image through projection or self-identification, case examples illustrate how the individuation process offers an antidote against a potentially destructive identification with another human being.