In the time before the first age, when the Gods were preparing to turn on their Primordial creators and claim Heaven and Creation for themselves they were working with Autocthon in the fashioning of the Exalted. Perhaps this early in the past the Unconquered Sun and Luna were lovers, perhaps this was a merely tactical move on their part or perhaps something Autocthon added in something to make the gods worry about the Exalted more then him as a precaution against further treachery but it seemed that the Solars and Lunars were made for each other.
After the war was won, solar and lunar started to marry between each other, forming such lasting bonds that they would endure throughout their lifetimes and into each incarnation beyond. There was more to it though, as everyone grew in power and explored their abilities some interesting and powerful secrets were discovered.
A lunar and solar mate could benifit from any lunar charm that was based on pack forming. Not only that, but through experimentation a new form of charm was developed between couples. A synergetic and co-operative power, these new charms were stronger then either solar or lunar charms. Very personal, highly dependant on the couple in question and disturbing to the Sidereals who had started to see hints of the darkness to come.
The end of the first age was here, the solars power dark and decadent. Their wives and husbands of the lunar exalted little more then slaves the Sidereals feared the effects of fighting the Solars while they still possessed this linked power. Working subtly they further fanned the hatred that was growing in the Lunar hearts against their once noble mates. When all was prepared the Dragonblooded rose up and the Lunars stepped aside. Seperated from their greatest allies, struck from all sides the solars fell. Those who had developed these sympathetic powers with their mates spat hatefull curses with their dying breaths on all their traitorous mates.
Death curses are a well known and fearsome power in the world of exalted. The Sidereals had prepared themselves against such curses, and had taken steps to gaurd the ones who would inherent rule of the world. They left the Lunars to suffer the ravages of the wyld and the hate of their dead loves. The time on the edge of the world was hard for the lunars, and harder for the lingering curses of their mates. Many died from dark circumstances but the strength of the Solars was not that of the primordials and as after the cursed lunar died any further incarnations was free of it.
Even today some of the first age lunars remember the curses of their Solar mates and what it did to their people at the edge of madness and chaos. The remember, but they do not hate them for it. They did betray their oaths, let the solars be pulled from their golden palaces and struck down by the armies of the terrestials. And they worry...did their mate curse them? Is the long departed spirit of a solar still hanging about them imperceptably waiting to inflict some darkness? The most frightening punishments are those you know you deserve but can not see coming.