Since I don't know the exact story, I can't say for sure. But it might have family members like parents, children, and grandparents as main characters.
Another theme could be unity. Christmas is often a time for family to come together, and if something runs in the family in the context of a Christmas story, it could show how the family unites around that shared element, whether it's a story, a custom or a value.
Well, actually there is a sequel. However, it might not have lived up to the expectations set by the first one. The story and characters might not have had the same charm.