People get so amazed at things like that but I don't understand why. Obviously it can depend on the animal's temperment but if they are raised together, they don't know anything different.
We had a tiny kitten once that we found. I kept it in what is now difficult child's room (it was pre-difficult child) and would bring it out when we were home so I could make sure Taz didn't accidently hurt it because it was so small. He would come up and sniff her and then go about his business. I had her out one day and she and I were on this chaise chair we have. Our cat jumped up not knowing the kitten was there, saw it, hissed and took off. Taz was across the room, saw this, ran over, sniffed the kitten over to make sure she was ok and then took off after the cat to "yell" at her. After that, I didn't keep the kitten separated. Somewhere I think I have a picture of the kitten sleeping either on top of Taz or curled up against him. We eventually found the kitten a home but for the time we had her, she belonged to Taz.