Should you leave Megaton after arming the bomb and return before detonating it, neither of the kids are present anywhere. Nothing in-game shows or confirms that they are dead.
The only child that can be killed in Fallout 3 is in Tranquility Lane, which is you. Eventually Bethesda scrapped the idea for The Elder Scrolls IV: Oblivion, but in Fallout 3 they have gone the other way, allowing children for realism, but making them invincible. This once again raised issues, because the tactic would undermine the whole point of children being there, which was making the game more realistic. Bethesda's response was to simply make the characters invincible. Bethesda faced a similar problem when making The Elder Scrolls IV: Oblivion, as they considered adding children to make the game more realistic, but this was controversial – if the children could be killed, Bethesda could be accused of making a child murder simulation.
If you kill them you get the Childkiller Reputation.Ĭhildren in Fallout 3, Fallout: New Vegas, and Fallout 4 cannot be killed. Children are killable in the first two Fallout games.