I do remember there being four basic classes of weapons, each with one that epitomizes it. I don't remember hearing those specific titles for them (grandfather, father, king, mother), animals, or "days to master" part, so that's interesting. I was just doing some web searching to see if I can find similar titles. It looks like at least two sites are using the same weapons, but with slightly different titles for them:
The Staff - The Father of All Weapons
The Broad Sword - The Marshall of All Weapons
The Spear - The King of All Weapons
The Straight Sword - The Gentleman of all Weapons
http://chinese-weapons.gungfu.com/ and
http://www.shaolin.com.au/weapon.html both say this and have descriptions of the weapons and classes. They also say that weapons can generally be traced back to five tools: the knife, the stick, the spear, the rope/vine, and the hammer/stone.
dmax999, you may have a point about the spear being difficult to defeat and in common use. But wouldn't staves have been similarly common and useable in the same manner? Our teacher noted that you could use a staff like a spear, for example by thrusting the tip forward in an attack. You're just lacking the spearhead on one end. I haven't trained with both, just the staff, but I've seen our teacher do some moves with the spear. I'm sure they're not identical, but they do seem so alike to me that I have difficulty seeing where the real distinction between them lies.