The Last Crimes of Peregrine Hind by Sierra Simone

Peregrine Hind, known to all as the bloodiest highwayman ever to bedevil the road, seeks only one thing—revenge against the Dartham family. And so when a robbery sends the second Dartham son and notorious rakehell Alexander Dartham tumbling to Peregrine’s feet, it seems like fate has given Peregrine his vengeance at last.
Except then Alexander offers him a desperate bargain: to kidnap him instead, so Peregrine can harvest a generous ransom from Alexander’s family first. Peregrine agrees, but he’s in no way prepared for a captive like Alexander, who insists only on the softest beds and the finest wines … and who enjoys being tied up a little too much…