OK, so I've heard stories like this one before, and I think I might be onto something with a particular hypothesis.

You know cuckoos, right? They're brood parasites, which means that the female doesn't care for her own eggs. She finds another bird's nest, dumps her egg into it, and when the egg hatches, it gets raised by the owner of the nest. A lot of birds don't even recognize a baby cuckoo as something different, so they'll just keep feeding it.

What I think is going on in these stories is that there's a species, perhaps very closely related to us, that's a brood parasite of humans. They use us to raise their offspring, the same way cuckoos use other birds.