I think they were once flesh and blood like us.
From encounters with "Them" I get a strong feeling they are people who live in a non-physical place and have changed much in their "less temporal" state. Their existence seems to be within the space we call our subconscious and they seem to be "soulless" and needing us to supply them with energy.
I understand a lot of that is conventional thinking.
Additionally, I think they are nephillim or hybrids of terrestrial and non-Earth origin and I believe "The Archons" lived at the time of Atlantis and somehow the fall of Atlantis is tied to their "dark ascension" to the astral plane. So they would be about 12,800 years old though ascending to the astral means becoming non-temporal.
Just some thoughts.