The Designer Child was a project that took place 17 years before the series main events, overseen by Macbeth Enterprises under the management of Takashi Kanda in parallel to a man-mind controlled interface to be used on Mobile Weapons. The plan was that artificially genetically modified children would be able to fit and perform better for the interface. Although never specifically said, the project likely came into fruition through the advanced computer Puck whom Kanda did use before coming into Masaki Kube's possession.
The Designer Child program however faced a major obstacle during the Kanda Incident where the company, its CEO and several parties were subject to scrutiny and investigation for charges of human right violations. The event caused the mysterious death of Kanda, upon which Kube a member of the founder family took over the company and Puck.
The Designer Children were supposedly taken under protection of different organizations, while the media and police ceased any further involvement claiming it to be to protect their rights after already being defiled. To present day nobody knows what truly happened to the children. While in truth they were all separated from each other, except for Amara and Moco who were at a facility in Hawaii at the time, thus being able to avoid the same fate.
After Kube took over the company, he had both children, aged between 7-8 years to go to Japan to be placed under his direct supervision. Kube had Amara placed and test a Machine Goodfellow specifically designed for him. The machine was then filled with Orgone Energy. Unbeknown to any party of the time, this caused the energy to flow into the consciousness of the Planetary Gear Amarok, thus reawakening the memories of the alien occupying the human vessel. Which upon awakening, assaulted the Daedalus Base in the moon, ravaging the lunar surface with a libido burst, killing all its personnel. Before Amarok could do the same to Earth, he was faced by Taiyou Manatsu who propelled himself on the Star Emblem which detonated himself along the Kill-t-gang. Although the threat was temporarily stopped and Taiyou was killed in combat, Amarok's Ego Block survived.
With his restored memories, Amara at some point performed a Telepath Kiss with Moco, reawakening her memories as Malkin. The two thus become loyal servants of Kube on the outside, while secretly using him with assistance of the computer Puck, who was in truth the control system of their mothership, to further their agenda to syphon the Earth's populace of their libido, killing them instantly and thus prolonging their existence.
Several years later when they all are aged 17. Amara and Moco would directly and indirectly awaken the different Designer Child, Alaya, Zin, Ai, Lin, Baku and Setsuna, in order to further their agenda. However at large due to the constant interference of Globe mostly that of the Midsummer's Knights, including the defected Alaya, going by the name Teppei Arashi, as well as the many Designer Children questioning both their immortal existence and their human existence, the assault on Earth became a failure.
The betrayal of Puck and his goal to install his own ego in every being of the galaxy, caused the Designer Child to sacrifice their immortality to defeat the monstrous Robin Goodfellow. This eventually ends with the Planetary Gear losing their immortality due to the lack of their Ego Blocks, thus making the Designer Children to become fully human.