Malcolm & Suzanne Rannoch novels

Nothing is fair in love and war. . .
Europe's elite have gathered at the glittering Congress of Vienna—princes, ambassadors, the Russian tsar—all negotiating the fate of the continent by day and pursuing pleasure by night. Until Princess Tatiana, the most beautiful and talked about woman in Vienna, is found murdered during an ill-timed rendezvous with three of her most powerful conquests. . .
Suzanne Rannoch has tried to ignore rumors...

"In the wake of the Battle of Waterloo, Paris is a house divided. The triumphant Bourbons flaunt their victory with lavish parties, while Bonapartists seek revenge only to be captured and executed. Amid the turmoil, British attache and Intelligence Agent Malcolm Rannoch and his wife, Suzanne, discover that his murdered half-sister, Princess Tatiana Kirsanova, may have borne a child--a secret she took to the grave. And Malcolm suspects there was more...