The Brahmins who became scholars of their time and were renowned in their society were called "Rishi" (Saint). The descendants of Rishi Atreya receive "Atreya Gotra". Those who have "kashyapa gotra" are the descendants of Rishi, Kashyapa and thus, the gotra of the Brahmins indicates who the forefathers are. Besides gotra, all four castes may have family names which are called "Thara" (subcaste). This family name was given later. Probably, the family name was given according to the place where they settled or the occupation they chose. People having different family names may have the same gotra, which indicates that their forefathers were the same. So marriage among the same clan is strictly forbidden.
As there were four castes in Hindu society, intercaste marriage was not allowed in order to keep the characteristics of a caste pure. Dominant and recessive genes were unknown at that time. It was based upon observation. When the Brahmin male or female marry with Chetri or Vaishya female or male, their offspring were placed in the Chetri caste. This was due to the fact bravery was thought to be a dominant character and cleverness a recessive one. Similarly, when a Brahmin, Chetri, or Vaishya married a Sudra caste member, their children became Sudra caste. The Aryans believed this maintained the family characteristics of the four castes.
Brahmins were to teach others. Being teachers, Brahmins had to become models of the society. Cleanliness was an important aspect of that. They cleaned their kitchen after every meal and the house each morning with a mixture of clay and cow dung. The adults of the Brahmin family bathed early each morning and changed into clean clothes. They had to clean the cooking utensils after each use and hang them over the hot stove to dry. They had a practice of drinking only fresh water. After the morning bath and after sunset, meditation was done. Brahmins were not allowed to drink alcohol, eat meat or onion or garlic. Fruits and cow’s milk were supposed to be consumed.
Brahmins were not allowed to own any land. Their work was to teach and work only for the welfare of the society. People from other castes had to provide food, clothing, and utensils to the Brahmins. For this reason, Chetri and Baishya caste members had to donate food every 15th and 30th day of the lunar calendar, and on festival days. Utensils and clothing were donated when a person died in that society. The earnings of a dead person not only went to the Brahmins, but also to the very poor persons of the society. Those earnings were also used to make memorials like paths, water taps, and public buildings, which could be used by other members of the society.