We were out for a walk today, and Sophia and Ethan had gotten ahead of the rest of us. As they approached a road, we called them back. Ethan stopped, and Sophia kept going. So Ethan went over to Sophia, picked her up, and carried her back toward us. Sophia protested in a way that imitated Ethan's usual protesting (which in turn imitates what his teachers say to him when telling him a general rule about not saying no to teachers or some such thing. Here is the exchange that began with that. The first line itself would have been funny enough, but she doesn't stop there.
Sophia: It's not ok to bring little people back to their moms and dads.
Me: Are you a little person?
Me: Is Ethan a little person?
Me: Is Bear-Bear a little person?
Sophia: Yeah, and so is Isaiah.
Me: Is the baby a little person?
Sophia: Yes, they are.
So she assumes a fetus is a person (whereas some philosophers I know might wonder if Isaiah is a person on their account of personhood, or perhaps they'd think his personhood is just now beginning to emerge now that he's beginning to communicate better). But she also thinks her stuffed bear is a little person. (In both cases it means she's working from a conceptual framework that doesn't require consciousness or the capacity for pleasure or pain for personhood. I'm not sure if there's some condition her assumptions about personhood require, though. I think for the bear she might be speaking in the world of her imagination or something.)
Then she does a third interesting thing. She goes on to use a singular 'they' with the correct grammatically-plural but semantically-singular verb (as opposed to saying "they is", which occurs in some colloquial English dialects even for a real plural "they" but not ever in standard colloquial English, which still says "they are" for a singular referent when gender is unknown). What's funny is that she and Ethan are in full disagreement about whether the baby is a boy or a girl. She wants a sister, and so she must be getting one. Ethan is expecting another brother. [We'll be happy if Isaiah thinks more of the baby than he would a stuffed animal he can throw things at, since that's exactly what happened the last time he was near a newborn. He nailed it in the head with a pretty hard plastic toy. That boy can really aim, but he needs some more discernment of targets.]
Anyway, Sophia isn't going to go out of her way to avoid using male or female terms for this kid. It's just so natural for her that she used the singular 'they' (and got it right) without thinking that she has this view she's putting forward about a baby sister. She's learned the language better than a lot of cranky language prescriptivists who think this expression is some offensive innovation in recent years (even though it occurs in the King James Version of the Bible, not to mention Shakespeare and Jane Austen).