Obviously those are two difficult cases. If you take North Korea, it's probably the most bizarre regime that currently exists in the world, the most Stalinistic in the worst sense of that. It is a very hard nut to crack in terms of expecting the usual sorts of international behaviour.
That said, I think there are pressures that can be brought to bear, and incentives, and through time a normalization of relations as part of an agreement to de-nuclearize the Korean peninsula is the best prospect.
As China has to assume greater responsibilities as a great power, there can be expectations that Beijing is going to have to be more constructive and assertive vis-à-vis its titular ally in North Korea, and exert pressure on them.