It's been a couple of weeks now & it feels like the two cats tolerate each other. My elder used to wrestle with my dog & both loved it. She doesn't do this any more but does pin, bite, paw and "rugby tackle" my kitten. She doesn't growl or hiss at all & it looks like play to me. Even though she does tend to bite his back & sometimes his boy parts hmy:. The kitten, however, acts differently. He is very vocal in general & tends to meow & sometimes hiss when she does this. Sometimes he will initiate it, sometimes he will go along but usually he ends up hiding behind my legs. They will sleep together, share food, share water, share company but my adult seems to want to play when my kitten does not. Usually, she wants to groom the kitten too & he does refuse this every time so she pins him to groom him. Now I am not sure when to intervene. When the hissing starts I make loud noises & they stop. It doesn't take much for the adult to leave him alone..