–Mariko Kurama to Doctor Saito, before lethally showing that parenthood is not just a title
Parents in Elfen Lied do not appear often, but usually have pivotal roles in driving the plot. Almost none of their given, or family names are ever revealed. The parents of main characters will have their own separate articles. A main character here is defined as a resident of Maple House.
Arakawa's mother appears in her visions after she is shot. Kurama is Mariko's real father, while Saito made the fatal mistake of believing Mariko saw her as a mother.
The clones of Mariko all had Kurama and his late wife Hiromi as their genetic parents, while Alicia, Barbara, Cynthia and Diana saw Nousou as their parent, at least while they had control mechanisms in place. Diana obeys Arakawa as a parental figure right before her death. The dying Cynthia recognizes Kurama, and while Barbara, after her release from control, does as well, she claims it makes her feel nothing but disgust at her connection to a Human, though her final action calls that into question.
Aiko Takada's father was abusive, and her artist mother abandoned but then considered reconciling with her before her death, with her mother very possibly alive as late as the series' finale, since Wanta passes a poster for her art show. Though Aiko's father had a girlfriend, Aiko made it clear that she in no way saw this woman as a parent. This woman was quick to mock Aiko's father after he was chastised by Lucy, and also quick to loudly accuse Lucy and Aiko of causing the father's death, the true cause of which the series does not make entirely clear.
In the series' final chapter, Kouta has a daughter, presumably by Yuka, whom they name Nyuu in honor of their late friend.
Even if Kurama acceded to Nana's wishes to become a couple later on, both were in effect sterile but could possibly adopt.
Whether Mayu overcame her intimacy issues (mainly with men) or not, children with Bando seems unlikely, unless he donated to a sperm bank prior to his ultimate maiming by Lucy.
So far as is known, Nozomi was fully capable of conceiving and bearing children.
Some fans have speculated, since the mother of Kouta's daughter was never named, that her mother could be almost any female member of the main cast. For the record, the younger Nyuu is the spitting image of Yuka at the same age.
Of course. At the Kaede House, Kouta is the father and you're the mother. That's how it feels like to me anyway.
–Mayu to a despondent Yuka, also showing that parenthood is not just a title