The Children are the four protagonists of Stranger Eons. They are all part of a group chat called "the htub". They seem to be of great significance to the Guardians with many eyestalks following them around. The children have a plan to meet up in Aminara Tower, due to it being the only landmark known by all of them. Each Child lives in a vastly different era and is confused by lifes of other Children. They all seem to be causally connected with the event.
Three of the children were shown to have arrived to their world on an asteroid:
Mars found a piece of rock and a news article talking about a a child recovered from an ████████ impact
Claw sent a photograph proving this claim, and Sepia recounted it with detail.
Ryann was explicitly told the story by Vekh and has seen a recording of this occurrence
Sari is unaware what an asteroid is, however being born from one would explain the absence of her parents.
They're called the Children due to their pictures showing them at a young age. However, most of them are young adults, and were around 13 years old when they emerged from their respective asteroids.