You should wait until your child reaches the age of five or older to get an animal. Let them know once they get this animal, it s their responsibility to take care of it and let you know as the parent when something is needed for the animal. Do not start off taking care of it for them, because they will not get into the habit that is needed by them to take care of their own animal. You needed to start them off by themselves on any procedures that has to take place to take care of this animal. This will teach them how to be fully responsible for the upkeep of their pet and will not have you involved.
Most parents start off doing it themselves and helping out.
This is the wrong thing to do, you want them to be totally responsible for their animal, since they wanted a pet and not you. That s why you, the parent, need to wait until your child is older so they can handle and understand what it takes to have any type of animal and how to take care of them. Pets are nice to have for the entire family to enjoy. If you already have a pet when your child is born, it s still your responsibility to take care of them. If you did not have any animals until you had children and they wanted them, it s their responsibility to take care of them.