Parental fitness is a child-by-child assessment expressed in terms of detriment to the child, which is a prerequisite to terminating parental rights, but need not be made at the section 366.26 hearing. Following removal of the minor and her younger sister, Mother participated in services and eventually reunified with the minor’s younger sister. The minor, who had more severe behavioral issues, was resistant to living with Mother and preferred to remain in her placement. A bonding study and other observations showed that Mother was dismissive of the minor and did not respect her boundaries. Additionally, Mother was a trigger for the minor’s troubling behaviors. At the section 366.26 hearing, the court terminated Mother’s parental rights to the minor. Mother appealed, arguing that the return of the minor’s younger sibling to her care rebutted any previous finding of parental unfitness. The Court of Appeal affirmed. Due process prohibits judicial termination of parental rights absent clear and convincing evidence of parental unfitness. Parental unfitness is a generic term to describe parents who have failed, refused, or neglected to provide proper or necessary care to their children. Under current California dependency law, the standard for parental fitness is expressed in terms of detriment to the child. While a finding of detriment is a prerequisite to terminating parental rights pursuant to section 366.26, the detriment finding need not be made at the .26 hearing. The detriment determination is made by reference to circumstances of the family, giving due consideration to the faults or shortcomings of the parents as well as the specific needs of the child. Thus, the dual considerations of parental capability and child needs require a child-by-child determination of parental fitness. Here, parenting the minor posed a greater challenge than parenting the minor’s younger sibling. Additionally, the relationship between the minor and Mother was burdened by a history of conflict, and Mother had failed to accept the minor’s particular needs. The record reflects a manifest difference between the siblings and Mother’s ability to parent each one. Mother’s argument that the younger sibling’s return to her rebutted or otherwise limited the viability of prior findings of unfitness regarding the older sibling fails.