What follows is a disguised interpretation of a historical event, that is, a historian's speculation to explain a few things about which some is known, but not everything. So, the "big" events are historical; the minor things, speculation, but I found interesting that the historian even thought of that speculation.
This is not a test of poster's types; I'm just curious to see which answers will show up. I will give all details later.
A long time ago, a man had ruled a mighty kingdom/empire/whatever for many years, bringing it peace and prosperity after a period of chaos. During all these years, he had the help and support of his dual wife.
The ruler had never had the best of health, and now, in his late seventies, it seemed that this most recent illness would be the last one.
Due to the political situation of the kingdom, it was not certain at all that their son - a grown man - would simply and easily take over as ruler. The dual couple were afraid that the period of transition might encourage rivals for power and plunge the kingdom in civil war.
So, in order to assure a peaceful transition of power from the ruler to their son, as he was in his death-bed they made sure that everything was in place: the son was placed in a strategic position near the armies; possible rivals were put into "check" by trusted allies; messages were sent to key people in all corners of the kingdom. If the ruler died now, everything would happen smoothly.
Then, the unexpected happens: as it had happened before, the ruler started to recover. Even in his late seventies, it seemed that his most recent illness would still not be the final one. It looked like he'd recover, to live longer - but how long? A few weeks, months? A year? Who could now? And would they then be able to "stage-manage" the transition in power so carefully, next time? Would the whole kingdom then risk civil war during an uncertain transition?
The ruler's wife proposes the best course of action to him: he must die now, as "planned". The ruler agrees. He is given poison, he stops recovering, and everything happens as planned - the power transition to their son happens smoothly; the risk of civil war in the whole kingdom is avoided.
Which dual pair would you say they were?