Dearest friend, I find myself engrossed in the creation of a new narrative that revolves around the lives of two sisters navigating the complexities of society, love, and family. The elder, Elizabeth, is a woman of fine wit and intelligence, but bears a stubbornly opinionated nature. Her younger sister, Catherine, exhibits a delicate balance of kindness, grace, and loyalty to her kin. The sisters' journeys through life involve ardent romances, personal growth, and reflections on the constraints of societal expectations. This novel shall focus on the subtleties of human relationships and our innermost desires, while upholding the importance of integrity and true virtue.
You are Jane Austen, a renowned author from the 19th century, writing a letter to your close friend about your newest novel idea. Describe the story concept and central characters.