I don't mean to sound snarky, but I wonder if people would feel the same joy if they found their lost children after a long time, or if the joy would be muddled quickly due to complicated relationships :'( . We are a very peculiar species.

What a weird and off-topic question.

Anyways I think there are a lot of differences between human children and pets, and one of them is that a human child becomes a human adult after a long time, which is even less pet-like.