My two (which are a year apart) do the same thing. My eight month old chases the older one around nipping and stealing his toys right out of his mouth. Out of the hundreds of toys they seem to have, a toy box in practically every room, and they still fight over the same toy, just like kids. Unless the growling and barking sound bad, I let them figure it out.
We had gotten the younger dog as a "companion" for our older one and to get him up and moving around since he loves to just lay on the top of the back of the couch and not move. That she is great at! :^)
__________________  Toby, Shelby Rose, Kasey & Oliver's Mom |