From A Wiki of Ice and Fire
The Two Kings is the nickname used to refer to Mern IX Gardener and Loren I Lannister, the last King of the Reach and King of the Rock, respectively.
During Aegon's Conquest, Loren I Lannister and Mern IX Gardener formed an alliance between the Reach and the westerlands in order to resist Aegon I Targaryen, the recently-proclaimed King of All Westeros. Together, they commanded an army of fifty-five thousand men, the mightiest host ever assembled in Westeros thus far. Their impressive numbers were no match for the dragons of the House Targaryen, however. Mern died in the Field of Fire along with all his kin from House Gardener. Loren survived the battle but bent the knee to Aegon the Conqueror the following day.
- ↑ 1.0 1.1 Fire & Blood, Aegon's Conquest.