Keep Families Together Act This bill prohibits an agent or contractor of the Department of Homeland Security, the Department of Justice, or the Department of Health and Human Services from removing a child who is under the age of 18 and has no permanent immigration status from his or her parent or legal guardian at or near the port of entry or within 100 miles of the U.S. border unless: an authorized state court determines that it is in the child's best interests to be removed; a state or county child welfare official with expertise in child trauma and development determines that it is in the child's best interests to be removed because of abuse or neglect; or the Chief Patrol Agent or the Area Port Director authorizes separation based on a documented finding that the child is a trafficking victim or is at significant risk of becoming a victim, a strong likelihood exists that the adult is not the parent or legal guardian, or the child is in danger of abuse or neglect. An agency may not remove a child from a parent or legal guardian solely for the policy goals of deterring migration to the United States or of promoting immigration law compliance. The bill sets forth presumptions: (1) in favor of family and sibling unity and parental rights, and (2) that detention is not in the best interests of families and children. The Government Accountability Office shall conduct a study of the prosecution of asylum seekers.