Children can't actually be psychopaths. They can be diagnosed with callous and unemotional traits that lead to adult psychopathy.
It is true that not all psychopaths murder but nurture is not the reason. A psychopath could have the best upbringing in the world and still go on to kill just because it took their fancy or because it was of benefit to them.
The whole point in a psychopath is they simply don't care. They don't have empathy, they act on impulse and don't care about the repercussions. You can't cure it, whether they become a surgeon or a murderer is mainly out of the parents control. There is usually a sexual element too which is why female psychopaths don't tend to kill as often and go more under the radar.
That being said there has been some sucsess with rehabilitating children with callous and unemotional traits through positive reinforcement. But there is no way of knowing whether those kids would actually have become adult psychopaths or just dysfunctional adults without the intervention.
I don't think we know enough about either RT or JV to say if either is a psychopath. But RT has seemingly got on with his life and stayed out of trouble, so it's more likely he was just a product of his environment. It seems quite telling to me that RTs older brothers were abusive to him and JB was of the same age and appearance as RTs younger brother.
Is JV reoffending because he's a psychopath or because he's disturbed by what he did? Who knows, but he's a pedophile which there is no cure, so in my view should be locked up for life. But that's not government policy.