I haven't had that problem with dogs, but I did with cats. When I used to have Snowball, and she was about four or something, my husband brought home Sally. Snowball hated Sally because now everyone fussed over her, and whenever Sally tried to play with her, she just walked away. It was kind of sad. Anyway, then Snowball ran away when she was about Sally's age, and to this day I still wonder if Sally ever remembers and/or thinks about Snowball. I bet she does. Now I am just going to go leave the room and wipe away my tears and think of happy things...I MISS HER SO MUCH!!