All great answers. The oldest child in a small family(2 children) have a glamorous role. He/she is the hip/cool older sibling that the younger sibling wish to emulate. He/she, although the oldest, is still a child and have a normative childhood & adolescence. He/she, although told to be the more mature one by parents, is not constantly inundated to ALWAYS be ON 24/7/365 like his/her counterpart in a large family(6 or more children) to be THE ADULT, THE PARENT.
Oldest children in small families are allowed to explore & enjoy their childhood. They are also treated on an equal parity with his/her younger sibling. They AREN'T cast aside like oldest children in large families are. They are given individualized attention & love by their parents who view them as human beings, not servicepeople. They are even indulged by their parents. It is not unusual for oldest girls in small families to be idolized & adored by their parents in opposition to oldest girls in large families who are ignored & unnoticed until they are called into service of their parents & younger siblings. Oldest children in small families AREN'T parentified children.