Kuu's Parents

Kuu's Parents are referenced little and are hardly seen at all. Despite being the parents of one of the series' main protagonists, the facts known about them reveal more about the series' shortcomings than about the characters themselves. According to Kuu, his parents abandoned him in a forest somewhere in Kamakura, naked and exposed to die, when he was only an infant. Found by authorities, he was turned over to the local orphanage. From an early age, both the staff and the other children treated the young girlish-boy with contempt, dismissal, isolation and outright abuse. How it is Kuu who came to know of this account was never revealed. It is equally possible that he asked when he was old enough to understand, or that someone at the orphanage learned of this and wished to taunt him with such harsh knowledge. In the anime, Tomoo explicitly tells him he heard he was found all alone in a field, meaning his origins were made known to the children, presumably by the staff. Though Kuu states he "no longer wishes to kill them," he otherwise doesn't express an interest in finding his parents for an answer, an apology, or revenge. Another question is who named him "Kuu," considering his abandonment in the forest as an infant. Unless left along with his birth certificate on his person bearing the name, "Kuu" is possibly a name assigned to him by the staff of the orphanage.
Absolutely nothing is known of the economic status of Kuu's parents, though the choice to leave him to die in such a state might indicate relative poverty and a lack of education. There is also the notion that Kuu was born out of wedlock to very young or otherwise unmarried parents, making disposing of him already an option in their minds. Another implication draws from the fact that Kuu's birth did not draw any attention, as birth oddities often do, meaning perhaps he was not born in a hospital. But this is empirical speculation, as the fact is very lately revealed in the series and only adds slightly more information to his hazy beginnings. All that's known is regardless of their economic situation, Kuu's mother wanted to keep the child, but the father did not.
The storyline of Chief Kakuzawa and his plans came to an end after his forces recaptured Kuu, and brought him to the underground grotto beneath the Special Children Research Institute. His intent was to convince him to join with him as Humanity fell, of which the Chief believed he and his family were members. To this end, he presented to him a young boy. He revealed to Kuu that this boy was his half-brother, born when Chief Kakuzawa captured, imprisoned and raped Kuu's long-lost mother, whose reproductive system was the only one besides his own capable of birthing children who were not sterile. For a variety of reasons, Kuu rejects this talk of an alliance, killing both Kakuzawa and his half-brother before departing the sinking island to find Jyugo.
It is in the details of Chief Kakuzawa's account that we learn some things and gain more questions as well. He tells Kuu that only his father wished to dispose of him. His mother loved im and once she learned what the father had done, began a years-long search that only ended when she was found and captured by the Chief. Notably, Kuu only has the briefest of reactions to this news. While he does make positive choices at the very end of the series, Kuu perhaps felt that the knowledge of his mother's love came too late to change things. Possibly it also strengthened his desire to see those he cared about once more, leading to his complete rejection of Kakuzawa's schemes.
While it is possible the father traveled a far distance to rid himself of the infant Kuu, it seems more likely he lived somewhere in the same area as the orphanage. In any event, an orphanage would be a prime place to begin a search for an abandoned child. As stated before, of course, Kuu's birth name and the name he had at the orphanage would most likely not be the same, hindering the search. However, he had at least two distinguishing and utterly unique features: his girlish appearance and his hair length (though hair is not always present on an infant). Adding to this, Kuu was a resident of the orphanage from his infancy to the time he was around 7-8 years old, had distinct features, and the staff was markedly indifferent to him and perhaps even eager to be rid of him. One possibility is that while Kuu's mother's search for him was heartfelt and sincere, it was not a well-conducted search.
A timeline problem or puzzle arises next, with the story of the mother's capture by Chief Kakuzawa. While ultimately not an insurmountable obstacle, it does have difficulties. Chief Kakuzawa tells Kuu that his forces captured his mother not long after they realized her existence. If the Chief's account is correct, Kuu's mother entered his clutches near to the same time as Kuu himself did, but there is no real indication of how quickly this happened. First, the Chief would have to know something about the girl he regarded as the Messiah, things like her name and where she originated. With the sanction and resources of the Japanese government, this would have happened quickly but not instantaneously, and even when they found the mother's name, her continuing search for her child would have made contact or capture at least a little slower, with her possibly not in one place for any length of time.
The time frame of Kuu's half-brother's conception and birth is another problem. To use the Chief's account, he should be no more than five to six, and if like his brother, not subject to double aging. At the side of the Chief, a very tall man, he already comes up to his father's waist. If the capture of Kuu's mother was not near to immediate after Kuu's, and if not pregnant very soon after she was taken captive, then a year or more must be subtracted from the boy's previously calculated age. Also, his ability to procreate with Kuu, which was Kakuzawa's intent to keep the blood line 'pure' would be in question for five to seven years more at the minimum. Other problems arise from this scenario, but the rape, forced birthing, and subsequent end of Kuu's mother's life are at least questions to be considered. Before his death, the Chief also informed Kuu that, while he intended to have more children with his mother, the woman found a way to end her life, which left his scientists scrambling for efforts to harvest her genetic materials and reproductive organs. Ultimately, their attempts were unsuccessful. Aside from the question of why the Chief thought to tell Kuu about not only his loving parent but that one's brutal imprisonment and death would purchase her allegiance, another issue comes with his lack of interest in Kuu's father. Perhaps, like many of the details of his ambitious plans, Kakuzawa failed to consider how the father would provide a complete genetic picture of the one so important to his schemes. Another option is that while Kuu's father did indeed offer half of his genetic makeup, his mother was far more useful since she could give birth to "Special" children instead of any information as to whether or not his father's genes could produce Special children. Due to the lack of any other fertile children like Kuu, his father might not have possessed the mutation if he ever had children again. Canon certainly never provides such information, and instead puts forth his mother as the one with mutated genes.
One ultimate impact Kuu's mother had upon him could be his final decision to save his friends and not destroy the world. Perhaps learning that his mother had loved him all along helped soften his heart just enough to turn back from the edge.
No images of any kind exist for Kuu's father. The ultimate fate of Kuu's father is not known, nor is it known how long into the series' time frame Kuu's mother might still have been alive.