Jenny is Jamie's older sister. She is the second child of Brian and Ellen, but their older brother William died when Jenny was about eight years old. After their mother died, Jenny took on the role of mistress of Lallybroch. She has a deep affection for Jamie and is very protective of him.

With Jamie's best interest at heart, Jenny sometimes takes a hand in his affairs. After he returned from his parole at Helwater, she was determined about setting him up with one of the widowed women of the district, and ultimately persuaded him to marry Laoghaire MacKenzie.