At first, a man making their own families lives separately. The peace and happiness of a family would depend on the unity among the members of the family. Observance of the principle of “Unity is Strength” is required every member to stand by the other in time of real need. This would require some sacrifice which would affect their personal interest and this loss of interest resulted in constant clash and quarrel among themselves. So a number of families in small groups were formed to avoid such unpleasant situation. There were also clash and fights among themselves and the small groups failed to protect themselves against more powerful groups. So they united themselves and a nation was built for greater security. This is the history of the formation of a nation. But a weak nation began to be tortured by the stronger one. So nations began to unite themselves for their safety and security.
It is very sad that we do not follow this principle in our personal lives. We indulge in quarrel with our relatives and this encourages our enemies to take advantage of this situation which brings our ruin. If we continue quarrelling and do not try to be united with one another one day may come when we will be completely ruined.
Happy to help.