Two bundles of grey fur. There are those who will say that animals do not have “personalities,” that they merely respond to your training. Try getting two. Siblings. Biologically, these two kittens are pretty close, brothers and littermates. When they first arrived, the primary difference between them was size. One was the runt and was just slightly over half the size of the other.

Now, he’s catching up. So much so that we sometimes have trouble telling them apart. Their markings are near identical–grey coats with a whisper of tabby. But you need only watch them for a few minutes to know who is who. The runt is bouncing-off-the-walls-batshit-crazy. He’s totally engaged, and addicted to his people. For him anything is a game, and he is up to the challenge. He follows us everywhere.

The larger kitten, Ollie, is mellow and reserved. Sometimes we wonder is he’s okay, but only because the comparison is so dramatic. He’s just fine. Really. We know that because he becomes fully engaged when he goes outside. He’s all cat–brave and intrepid, exploring the property, even in deep snow. It’s not even that he’s shy inside, but next to Mr. Personality, he seems so. He’s just a softer, gentler version.

Obviously, these doppelgängers have the same food, the same environment, and similar genetics and yet the differences are marked. We don’t think that we contribute to the difference in how they’re treated (although that little guy sometimes requires self-defense maneuvers.) So, innately they must come pre-wired with different characters. Not so different than the rest of us.