The Sheikh's Secret Heir (Harlequin Desire Book 2380)

She's about to have the sheikh's baby! 

Tasked with entertaining a mysterious billionaire, Bajul diplomat Kira Darzin never expects her assignment to extend to the bedroom. But one look into Tarek Azzmar's smoldering eyes and she's helpless to resist. Now her unplanned pregnancy—and Tarek's secret identity—threaten the royal family she holds dear… 

The illegitimate son of Bajul's former king, Tarek vows revenge on the father who rejected him. And Kira is a complication he can't afford—no matter how the sultry beauty challenges him. But when the truth about his past is revealed, will Tarek lose Kira and his unborn child for good?