Empathy is critical to your child's future.
Empathy is the ability to see the world through somebody else's eyes and to experience, meaningfully, their feelings, thoughts and wishes. In my own language — to step into somebody's shoes, to wear their skin on your body for a while.
Now: how can parents make their children empathetic?
Contrary to the cliché, love is not the answer. Or more precisely, warmth and love alone are not enough.
What develops empathy is clear and consistent boundaries.
That sounds counter-intuitive, so let me lay it out.
A child who has never encountered a limit has never encountered evidence that other people have an independent existence. That is not a moral failing on his part; it is an information problem. From inside his experience, the world simply reconfigures itself around his wishes. There is no observable reason to conclude that anybody else has needs, because no need of anybody else's has ever made any difference to anything.
A boundary is the first hard evidence that somebody else is real.
You cannot have that now, because your sister is using it. We are leaving now, because I have to be somewhere. No, because I am too tired.
Each of those is a small, concrete demonstration that another person has requirements which do not bend, and which have consequences for him.
That is the raw material empathy is built from. Not from being told that other people have feelings — which is an abstraction a child can repeat perfectly while understanding nothing — but from the repeated experience of encountering somebody else's needs as an actual feature of the world.
Which is why the warmest households sometimes produce startlingly self-absorbed adults, and why the instruction to be endlessly accommodating is not the kindness it appears to be. A child who learns that other people have needs, feelings and entitlements learns to take them into account.
He cannot learn it from a household in which nobody's needs ever cost him anything.