In people's minds, people who are related by blood are much closer than those who are not related by blood, such as aunts, uncles and aunts. They are all brothers and sisters of their parents, and the relationship is naturally very close. And they love their nephews or nephews very much, which can be said to be like loving their own children. But uncles, aunts and uncles are different. They have no actual blood relationship with themselves and joined this big family later, so they don't feel so close. And if you live far away, there is basically no contact at ordinary times. Therefore, there is a saying in the countryside that "an aunt is an aunt and an uncle is full of bullshit".
The origin of kinship terms can be traced back to the ancient countryside. As the saying goes, three generations are inseparable from farmers. No matter who they are, their ancestors may have been farmers before. We know that farmers live in a relatively concentrated place, and most farmers live in the same place for a long time. When people are familiar with it, they naturally have appellations, especially the generational relationship with relatives at home, so there are various origins of kinship appellations.
Although this proverb says that people have three relatives and points out who these three people are, the similarity of these three people is that they are not directly related to us, which is very realistic. But in real life, we really don't kiss uncles and aunts, and it's not all true, so this can't be decided directly.