Courting a Spinster for Christmas: Sweet and Clean Regency Romance (His Majesty's Hounds Book 16) by Arietta Richmond

This is a romance about an older couple. Two people who have much in common, but never had time for marriage. These two are lonely as they approach fifty. They are spending alot of time together to research the history of the Seddon de Hirst family tree. They find they have more in common than history and room for love. This is well written without the intense passion of a younger couple, but written with thought to the couple's maturity and their respective careers.