What was his personality like? He looks like a little bear!
He actually wouldn't be inconsistent with the kinds of cavaliers that can come from BYBs and puppy mills -- you will see a huge variation in size, head shape etc. Some cavalier lines way back when were actually developed using springers amongst other breeds (Bet would know all this in more detail) so you do see some odd and unusual features come to the fore sometimes. From viewing dogs on Petfinder a lot of the cavaliers look more like crosses.
The other issue is that many cavaliers from such backgrounds and used for breeding may have other breeds in their background more recently and this might emerge when other less than scrupulous breeders breed these dogs in turn.
I've seen some pretty odd looking cavaliers come from club-registered breeders too -- way off breed standard. That's why club registration on its own doesn't necessarily indicate a quality breeder. Research, research, research for the puppy buyer!