I am actually fascinated by mom/sibling relationship. Lily treats Sully very differently than she did Rhum when she was a pup. Lily is very much a ruff-n-tumble type of girl but she is very gentle STILL with Sully and lets Sully walk all over her.Mom let her win
Have you noticed that this is true too? Ruby plays with Gin, but always gives Gin the upper hand...not at all how she plays with other dogs. And Gin leaves all confident and self assured!