The three most common populations in the Franklin Universe are actually Dogs, Rabbits, and Sheep, while the larger populations of other races, of course, are around, but strangely are not generally found in huge numbers in the Victorian Era based series. This leads to the nobles & the wealthy seeking out ways to make themselves more varied from the others of their ilk. This is why Witches, Warlocks, and people with knowledge of magic are a dangerous past-time for them. (and a "worst kept secret" among the wealthy)

The Fox Family after all isn't the only family out there with magical potential and some families do carry a smaller variant of the spark of magic, or as a few would call it "an ember seeking some air to light into a blaze"

Granted not every family that can work magic is Honorable as well, and some merely give the illusion of assistance as they merely seek their own amusements at others' expenses.

But almost all the magic families seek those with the "ember or spark" for magic, after all, one never knows how strong it could become if it were to lite by itself without supervision.