My DD is almost 17 years older than Charlie and had a hard time getting used to having a baby in the house again. She didn't like not being able to have friends over at night anymore because Charlie was asleep, and because she worked nights, we fought a lot about her coming home at 3am and making a racket. She ended up moving to her dad's when Charlie was a few months old. Since then things between us have improved (there were a lot of other issues mind you) and she now comes over at least once a week as she doesn't want to miss Charlie growing up, and is very much his sister in every way atm.

My DS1 was 14 when Charlie was born, was already living with his dad, and while he genuinely seems to have an affection Charlie when he sees him, he doesn't see him very often. As he's gotten older, he's become less involved with any of his family and more involved with friends, as they do at this age. Charlie isn't overly attached to him like he is with his other siblings.

My DS2 is 13, was 11 when Charlie was born, and lives with us. Charlie adores him and he adores Charlie. They spend hours playing in the afternoon after school, and my DS2 loves having a baby brother.

So I think it really depends on the effort put in to be close the the child. My DS2 could have been sullen and withdrawn with the arrival of the new baby, effectively taking over the spot of 'youngest child' but has really embraced being big brother. My DD is trying to ensure she has a bond with Charlie, and my DS1 isn't trying very hard at all. And in time to come, I guess this will shape their relationships with him, and with each other as well.