It depends on which pet you're breeding with, if you're breeding with any pet, you have a chance to get your own pet, or the other persons pet. So far you seem unlucky.
Hello! That is unfortunately how the pets work. A stray piggle is a common pet and so when you hatch with something more rare you have a higher likelihood of getting the piggle. I would suggest you just keep hatching with the exact same pet over and over and level the piggle to adult each time so you can increase your stats and the chance of getting the talents you want. So by the time you do get the pet you want you will have great stats and talent pool. Hope this helps.
It might be just random luck. My first 3 hatches, I got my same pet, but with better pedigree and powers it could get. When I got the other pet, it was with one that was about the same pedigree as my pet. I think it was just a random thing. At least, you are improving what those piggles can do. Try training the best seeming one, see what it gets, and then use that to hatch. Eventually, you will get another kind of pet. If your stray piggle picks up some nice powers, you might even find someone willing to use the hatchery with you, which would create possibilities to get pets that aren't in the kiosk.