This HaBO request is from MelKelCan, who wants to track down this romance:
Once upon a time I read a historical romance set in Scotland (I think?) where the heroine was married to a lord of some kind, who became ill and progressively lost control of his legs. They discovered that he would be unable to father children, or even have sex.
At some point, a third character entered the scene, possibly a former laird of a clan, who was big and brawny and the husband suggested the heroine “lay with” the Scot for some baby-making. Eventually the heroine fell for both men, multiple children were born, and the husband’s health deteriorated until he died—leaving his title to the first born.
Ring any bells?