Much of what we can discern about William fitzHerbert's life and career revolves around his family connections. His father, Herbert the Chamberlain, was instrumental in securing his appointment to the treasurership at York, and William maintained links with other members of his family until the end of his life. The churches which he acquired derived from his family's estates, and he probably maintained an interest in some of the family properties, particularly those in Yorkshire, throughout his life. The evidence of direct relevance to William himself has been discussed at appropriate points in the preceding chapters, but much of the evidence only makes sense in the light of occasional references in widely dispersed documents, often of much later date. By assembling it into some sort of coherent order, it has proved possible to illuminate the family and the estates of one of the most successful of the royal officials at the court of the Norman kings, and their descent. I shall consider firstly Herbert the Chamberlain's family tree (Genealogical Tables 1–3), and secondly his estates.

William's father, Herbert, was chamberlain to William the Conqueror, William Rufus and Henry I, and his career has been outlined above. But there has been no consensus about his origins. John of Hexham states in passing that William fitzHerbert was a kinsman of King Roger of Sicily. John was writing only about a decade after William's death, before the emergence of the cult of St William, and is considered a generally reliable witness. William of Newburgh, another well-informed northern writer of the end of the twelfth century, says that William was of noble extraction. Neither author, however, expatiates further on his family. The early thirteenth-century Vita of St William asserts that he was the son of the most powerful and energetic Count Herbert, and very similar wording is to be found in two versions of the later-fourteenth-century continuation of the York a count, and William of Malmesbury, in his account of Herbert the Chamberlain's attempt on Henry I's life, states that the ringleader (whom he does not name) was a man of low birth who rose to fame in the royal treasury. Such eminent authorities as Bilson and Hollister have dismissed the York evidence as worthless hagiographical invention.