In the Dokushinkizoku no Kake series (独身貴族の賭シリーズ): 594b

1) Persuading the Playboy King by Kristi Gold (2004)
Breathless, Dr. Kate Milner couldn't help but stare at the King of Doriana and the electricity they'd shared in college. Years later, she was working in his clinic and found herself wanting to strip Marc of his regal robes and rediscover the man she'd once known.

Newly crowned king, Marc DeLoria had a dilemma that compounded daily. Did he give in to his primal feelings for Kate -- and become tabloid gossip -- or show himself as a strong, saintly ruler? The more time he spent with Kate, the more he realized that not only was the crown in jeopardy...his heart was in the greatest danger of all!

2) Kodoku na Onzoushi / Unmasking the Maverick Prince by Kristi Gold (2004)
Her assignment was to interview millionaire Mitch Warner, the Maverick Prince of Oklahoma, not to sleep with him! But the confirmed bachelor soon had Tori Barnett entering into a scorching affair that hadn't been part of her agenda.

Nor had she counted on the unexpected result of their union....

When Mitch made a bet that he wouldn't marry for ten years, he hadn't counted on meeting someone like Tori. The brown-eyed beauty had branded him with her white-hot kisses and had him contemplating commitment. Yet he could tell she was keeping secrets, and the man who had been burned too many times wondered if giving his heart to Tori meant the world learning of his every desire. [Taken from FictionDB]

3) Sabaku no Meikyuu (Desert Labyrinth) / Daring the Dynamic Sheikh by Kristi Gold (2004)
Fiery beauty Raina Kahlil was content until her long-absent fiance, Sheikh Dharr Halim, came to whisk her back to his kingdom -- to visit her family, not to marry her. Deep down she ached for the playboy prince, but tried to resist the palpable heat between them. Yet as his fevered touch fueled her desire, she realized she'd been saving herself all these years...for him!

Dharr prepared himself for his eventual marriage to Raina and tried to warm her to the idea of a loveless union. But at each turn she dared him to unravel his guarded heart. And the more heated their encounters became, the more he lost all reason -- and ran the risk of complete surrender to her... [Taken from FictionDB]