Academics questions if morality is learned or natural. Empaty is a common attribute between animals, so we could arguee that making no harm to others is written in our dna. However selfishness is also a general sentiment, it makes us protect everything that is ours. So the parents are the ones responsible of teaching the children how to correctly behave. Teach them to share, to forgive, to ask for permission… Morality goes beyond the nature. There are many rules and laws invented by the societies. Hence, the older the children, the better he diffierence between right and wrong behaviour.
Nevertheless relatives can also give a poor example. Children most of the time do not distinguish between right and wrong, so they just imitate the grown-ups close to them. This way, family can be the most impactful influence in the morality of a child.
Not only the family shapes the morality of a child, the overall environment also desides which behaviour codes he is going to follow. It is not expected the same behaviour from a lower-class uneducated children from Urzbequistan than from a rich French children that went to the most expensive school in the world. The people that arounds them will have different lives codes.