Most textbooks consider Stephen the last Anglo-Norman king because, as they say, he was the last king directly descendant from William the Conqueror. (e.g. Hugh M. Thomas, The Norman Conquest, 2008) However I don't see how Stephen's lineage (being William's grandson through his mother Adela) was really any different from Henry II's (William's great-grandson through his mother Matilda)?
Am I failing to see something very obvious here or are there better criteria for seeing Stephen as the last Norman king, such as the rise of the Angevin empire and Normandy's subsequent relative decline in importance to the kings of England perhaps? Many thanks in advance!
You hit the nail on the head in your last sentence: it is more due to the rise of the Angevin Empire that historians see Stephen's reign as the end of an era. You are right that their respective descents aren't all that different. But the beginning of the Angevin Empire really changes things so much that historians like to mark the divide there with different nomenclature.