The most important theme throughout No Great Mischief is family. Whether it is the personal relationship between brothers or the more sprawling, complicated network of clann Chalum Ruaidh, almost every event in the book is portrayed through the lens of its effect on the family. In both the past and the present, Alex spends most of his time thinking about family and how to help his brothers, his sister, and his grandparents.

There are two different types of family members in the novel: those who are alive and those who are dead. For the latter, there is an obligation on the part of the living to remember them. Every dead person is kept alive through shared stories and anecdotes, whether it is Calum Ruadh or Alex’s mother or even the dog, who is shot by the replacement lighthouse keeper and thrown into the sea. The living remember the dead family members and frequently remind one another of their lives, preserving their memory for as long as possible. Physical manifestations of this memory—such as Calum Ruadh’s grave or the dedication Calum and his brothers drill into the rocks—are static; the real family history is an oral tradition, passed down between generations.