Growing up I did not know what a vegan was. My sister decided to be vegetarian when I was between ten and twelve (around 1980?), I guess – so I’ve got 30+ years of experience in this realm. However I’ve only had a plant-based diet and had a serious interest in animal rights for for a few years – since I was around 40.
With little warning but lots of support our three kids have grown accustomed to this world where pets are the only animals that are safe. Obviously there are many other families who have to explain to their children why people eat animals.
Here is a thoughtful essay on the topic: https://vegfamily.com/innocence-lost-explaining-veganism-to-my-daughter/