I don't quite understand the concept of "hatching" a pet. Does it make a new pet or does it just make the stats higher?
yes, it makes a new pet. and if you hatch with a partner it gives a new pet to each player. however if you had two mega pets and hatched a new one you would still get a baby that you need to train all the way back again and once you train a hatched pet it should get a combination of talents (i'm not sure if it's from the five talents it got or would have gotten or from the ten in the pet)