Our 8 year old doesn't remember life before her siblings. She was 3 when they were born. To her it's like they were always here. She doesn't even remember her 4th or 5th birthday parties. But starting around 5.5 years old she remembers a lot more.

Our niece supposedly remembers life before our oldest. She was 3 when she was born. I think a big difference though is she had the continual disappointment from then on of not being the only grandchild.