If you have a pet that doesn't get the talent that you want for example my frankenbunny didn't get energizing battery can you hatch it with another pet to get it?
Yes. When I got my Betta Fish, it failed to get Energizing Battery. I just kept hatching from the original failed pet, because the talent was still in it's pool. After several tries I finally got Energizing Battery to appear in a hatch.
If you hatch with another pet that has "Energizing Battery" discovered, your chances of gaining this talent on the offspring will increase greatly. If the pet has it, but the player hasn't discovered it, then the offspring still has a low chance of getting "Energizing Battery". I hope this make sense. Remember you can still get this talent if your pet isn't leveled up all the way. But rarer talents are harder to get as your pet levels up (I think) so it might not be worth it.
If you hatch with another pet that has "Energizing Battery" discovered, your chances of gaining this talent on the offspring will increase greatly. If the pet has it, but the player hasn't discovered it, then the offspring still has a low chance of getting "Energizing Battery". I hope this make sense. Remember you can still get this talent if your pet isn't leveled up all the way. But rarer talents are harder to get as your pet levels up (I think) so it might not be worth it.
Having a talent discovered doesn't really increase your chances. Having the talent whether discovered or not on both pets increases your chances only because it's 2 of 20 in the pool instead of 1 of 20. Rarity of talents doesn't matter on when talents appear; they can appear at any stage of training.
As long as the pet has the talent in its pool then it still has a chance of getting the talent. To get the talent though, you must train a pet that has it in its talent pool until it gets it. There are guides you can search on google and youtube on how to make your perfect pet.