A Harmony of Fire and Earth. Elemental Magicae, #2

Prince Edmund of Thalassa and Prince Arden of Aither are eagerly anticipating their upcoming wedding, but the danger to their kingdom hasn't lessened. They have a plan, but they won't be able to carry it out alone: they need a strong wielder of each Element, whom they can trust implicitly, to carry out the magic. Rhys is a commoner and wielder of Earth magic. He and his sister have made a living from the use of their magic for years and have become highly respected in scholarly circles, though he prefers a more simple life with his plants.
When a message from Prince Arden reaches them asking for their help, they don't hesitate. They stop only to request that Gaz, a strong Fire wielder and the man Rhys has long been enamored of, accompany them on the journey to Thalassa's royal palace. What no one knows is that Gaz was once known as Prince Gareth of Thalassa and is Edmund's younger brother, long believed dead. He fled his home after his Fire Affinity made itself known and put him in danger, and he had no intention of ever going back.
But he can't keep himself from going to his brother's aid, despite the risk of discovery and of the weight of his secrets potentially crushing his fledgling relationship with Rhys. Working against time, they must find a way to come together in a magical working the likes of which none of them has ever imagined, or their homelands will surely burn.