Although Kaworu is classified as an Angel, he is actually more similar to Ayanami Rei in being a Seed of Life that inhabits a human body. Kaworu does not consider himself to be human, however, as he refers to humans as “the Lilin” of “spawns of Lilith”. It appears that Kaworu’s body was created as a result of the Contact Experiment with Adam, wherein DNA from an unknown human donor dove into and fused with Adam’s flesh. SEELE salvaged Adam’s disembodied soul into Kaworu, whom they had recovered in embryonic form in Antarctica.
Source: Finnian菲尼 on World Cosplay