In medieval times, a divorce was almost impossible to achieve. There were few grounds, but even should a divorce be granted, it resembled a legal separation in modern times. When a couple were married, by law they were obliged to live together and certainly to have sex with each other. Sex was the legal right of both parties and the church had the power to order a couple to live together if they had parted. King Richard I, well known for having failed to consummate his marriage to Queen Berengaria, was eventually ordered by the church to return to his marriage bed.
A divorce was the legal way of putting an end to such interference so that a couple could live separately if they so wished, but they were not usually free to remarry. An annulment meant that the marriage was never valid in the first place.
That being the case, I have entitled this novel The Viscount's Divorce, because The Viscount's Annulment just doesn't have the same ring to it! I hope you will forgive this creative licence. Book three will be about the youngest brother, Viscount John, and will be coming soon.