Children of Promise are children who were taken from their rebel parents at a very young age and forced into a government program without their own knowledge. They're seen as being more robust, adaptable and capable than their peers. This is because the government believed the genes which allowed their parents to come into leadership of rebel factions due to their superior intellect and strength must have been passed down to them. Although some of the few people outside the Government with knowledge of this secret program believed that, in the end, the Government deluded themselves into believing some of these children had capabilities simply because they wanted them to have them.
The government had a plan to train Children of Promise from a young age to eventually defend them from the forseen battles that would inevitably be born from the paranoia and growing tension between the upper and lower classes. It was obvious that these children had to be young enough to be manipulated and couldn't be stray orphans from the lower classes; they had to be sure they were fit enough to cope with the rigorous training and testing that would come with age. Nobody in the higher levels of the City wanted to give up their own children for the cause of defending the City and the Government grew more desperate. After it became evident that nobody would give up their child for the plans that the government had, they forcefully started taking children from the strongest revolutionaries within the lower levels.
There were originally nine Children of Promise: a couple proved incapable of coping with the rigorous training and were eventually cast back into the lower levels as orphans and some were killed in testing and suit malfunctions. Eventually only four remained. Olivia was the first, after her came Oz, the next was killed in combat and the last commited suicide due to the growing pressure put on her by the Government. After the death of the last Child of Promise, the CoP program was shut down for good.