Once a Pirate by Diana Bold

A broken bond...
Talon Montgomery has no reason to love his family. The illegitimate son of a wealthy earl, ignore by his father and out of touch with his brother, he has made his own way in the world as a privateer. When he is arrested for piracy, he desperately reaches out to the earl for help, only to be offered a devil's bargain: Seduce his brother's wife in exchange for the lives of his crew.
A neglected bride...
Lady Katherine Sutcliff has been married to Talon's brother for two years yet has never spent a night in his bed. Unhappy and isolated, Katherine never expects her father-in-law to go so far as to barter her to his illegitimate son in order to produce an heir.
When she reluctantly finds herself on a voyage to America with her husband and his brother, Katherine finds herself in the middle of a dangerous game with no idea that she is about to lose something far more precious than her virtue.
A borrowed wife...
When Talon agrees to entice his brother's wife, he never expects to wind up fighting for her heart. Now Talon's carefully constructed plans are about to come tumbling down, for God help him, the unthinkable is occurring-he's falling in love.
Although her husband's false vows have already dashed her dreams, Katherine instinctively trusts his brother. But as the beguiling pirate wreaks havoc on her-body, mind, and soul-what will happen when Talon's deception is uncovered?
And what if Talon refuses to relinquish his borrowed bride, no matter what the cost?