Why do older people give names according to their sects? Please introduce in detail

Since ancient times, there have been common sayings in our country that "having more children brings happiness" and "having children and grandchildren brings happiness". Therefore, in the past, only sons and daughters were rare, but the phenomenon of having many children was extremely common. In addition, there are many close relatives and brothers and sisters. In order to show the prosperity of the family, they always have to be connected by name. In this way, when naming, the method of ranking brothers and sisters is very particular.