u/buiskitt

I have two fully black cats, brother and sister. The girl Cassiopeia, has a small white patch on her tummy. Both have a few odd white hairs here and there. Those are all normal for a black cat. But the boy, Perseus, has an odd grey marking on his back leg, that I have never seen before. I'm wondering if anyone knows what genetics might be causing this. It is only on his back right leg, nowhere else on his body. Is it just seeing the tabby underneath? But then why is it only on one leg? I included a handful of photos. In the photos, it also looks like it is on the base of his tail and his tummy, but this is not noticeable in person.