Taming Flame by Therisa Peimer

Flaminius's days of bouncing between beds are snatched away the instant he sets eyes on his perfect genetic match, Aurelia. Suddenly, the tedious task of claiming his rightful place on the throne of Arkhnuet doesn't seem as daunting with his whip-smart wife by his side. But it's not like Aurelia had a choice; Flaminius is the only soul she can reproduce with, and she's not about to play a role in her people's extinction.

After a swift wedding and passionate honeymoon, an assassination attempt plummets the lovers back into the reality of ruling. Fueled by their indomitable matched hormones and fierce loyalty to each other, together they must evade his mother's Machiavellian schemes, hunt down the mysterious cause of death among the match-making Keys, and protect the people from a violent supremacist cult, the Oradagra. But it turns out that the greatest threat to their existence is something neither of them could have seen coming, and it's a race against time to save the entire Arkhnuetian planet.