The Denning family's occupations over the generations could be key. If they were mostly farmers, then their farming practices, the land they worked on, and how they coped with good and bad harvests would be important parts of the story. And of course, any family secrets or legends that have been passed down would also be key elements.
Locations could be a key element. If the Denning family has lived in a particular place for a long time, that place becomes an important part of their story. Also, important events like weddings, funerals, or big celebrations are likely to be key elements in their family story.