bond between siblings

One day while I was on my way to work, out of the corner of my eyes, I saw a pair of figures moving steadily towards my direction. It is really early in the morning and the height of the figures is not what I have expected at that hour.
I took a second look, another look and another look.
It was a pair of sisters, holding hands, walking towards me.
Both of them are in uniforms.
The older sister who wore a primary school uniform, was probably in Primary 2.
The younger sister who was skipping her way to school, was probably in nursery.
Upon seeing them, I wondered where are their parents? How come they are so comfortable letting the two young girls to fend for themselves and go to school on their own.
I searched around. There was no adult figure around them.
I was a bit worried.
What kind of parents allow children of this age roam to school on their own?
By the way, at around 720am in the morning, the elder sister was probably late for school.
I keep observing them, trailing behind.
Then I began to see why the parents did not follow.
The elder sister was very responsible.
When her younger sister was going to let go of her hands while skipping her way, she restrained her and stop her from skipping.
The little girl, all cutesy looking, obeyed her sister and started to walk.
The little backpack she was carrying, was swinging in a regular rhythmn, left right, left right....
Very cute looking.
The sister looked out for incoming cars and led the both of them to the other side of school.
I could feel the deep bonding between the two of them.
The kind of bonding I longed when I was younger.
When I heard that mum was expecting, I was telling myself, I wanted to take care of my younger siblings in the same manner as the elder sister.
 Shield them, protect them.
Didnt come out the same way as expected.
But I felt strongly for that kind of bonding.
Afterall, how many siblings can you have in a lifetime?