Yikes, that sounds like quite a dilemma. When my sister was young she couldn't really do the sibling rivalry thing because we were so much older than her. It was pretty crazy having 2 kids in college and one in diapers. She still managed to have sibling problems with the DOGS. My dog is an attention hog and the two of them were always competing for attention. I used to walk in and find my mom in a big chair reading with my sister under one arm and the dog under the other.
Every man dies, but few truly live. Live your life to its fullest, every day as if it were your last.