Jin means unity, happiness, fruitfulness, and both ability and political integrity.
Everything will be prosperous if the family is harmonious, which means that a harmonious family will prosper. Source: Strange Current Situation Witnessed for Twenty Years_Chapter 87: "Generally, a family must live in harmony. It has always been said: 'Everything prospers when the family is harmonious.'
"The Analects" also says "Harmony is the most important thing when it comes to etiquette." When people live in this world, they cannot live alone without the society.