The Grace family is a related family to the Spiderwick family. Just like the Spiderwicks the Grace family lived in the Spiderwick Mansion and had the same fate as the Spiderwicks. Judging by the only members of the family that were seen, the family is probably very small. this is also the family of Jared Grace, Simon Grace and Mallory Grace. Some related families would be the Spiderwick family.