we may only have 10 family types in MoP for pet battles but within those type are sub-types which are like their own family. Here are the sub-types i can see from the data gathered so far:
1. Elemental - Fire [Phoenix hatchling, Searing scorchling, Lil' Ragnaros etc.]
2. Elemental - Earth [Pebbles, Golems etc,]
3. Elemental - Plant [Singing sunflower, Withers, Teldrassil sproutling etc.]
4. Flying - Birds [Owls etc.]
5. Flying - Bugs [Moths, fireflies etc.]
6. Undead - Plague [Bats, Infested animals]
7. Undead - Ghosts [Ghostly Skull, Lost of lordaeron, Restless Shadeling etc.]
8. Beasts - Poison [Snakes, Scorpions etc.]
Each of these subtypes seem to have their own type of abilities within that family, for example Fire is only used by the Fire sub-type in the elemental family and not by the plants. This means we could possibly have over 20 sub-types to play!
Can you name any more sub-types?