Brahmins a part of Santana Dharma have branches and subcastes.
It may be noted that Caste is a loose translation of the Term Varna, which indicates disposition(even this term is not an exact translation)
It has nothing to do with race.
Brahmins, an essential part of Santana Dharma, were spread throughout India.
Brahmins, as in the case of the other varnas(Castes) were a single community.
However over a period of time, there evolved a division among them based on the Sutras they follow and later Geographical location.
Astasahasram, a Group of eight thousand Families,
Vadama, who settled on the northern banks of River Cauvery,
Vaathimaa, most of this group were engaged in Proestly duties, Purohitham.
Bruhatcharanam. it is believed that long time back a family of Brahmins were accused of Brahmahathi, that of killing a Brahmin.
They were ostracized by the Brahmins.
Then they performed a Yagnya, Bruhat Yagnya, to purify themselves.
Then they were readmitted into the Brahmin -fold and hence the name Bruhtrcharanam , now called Brecharanam.
For example, there are Shaiva Vellalars,Kaar Vellalars,Karai Vellalars in the Vella community.
The term Vellala in Tamil means one who regulated Flood.
One who regulates Flood is Vellala.
Among them who minds the Bund are Karai Vellalas.
Kaar Vellalas are those who regulate the flow of Flood at the time of Rainy seasons,Kaar in Tamil means heavy rains.
Among all these those who do not eat meat are called Shaviva Vellalas.
Similarly those who follow the six duties assigned to Brahmins, are Brahmins.
The six duties.
Yajanam Yaajanam Tathaa
Daanam Pratigraham Chaiva
Learnng the Vedas,
Teaching the Vedas,
Perfoming the Yagnyas by themselves,
Perfoming Yagnyas for the others,
Accepting Gifts and
Donating the needy.
In addition they must have realized Brahman.
The Vedas contain branches, called Sakhas.
Please read my post on Vedas.
The Veda mantras are , most of them aphorisms, especially in Brahmanas and Upanishads.
While the Upanishads speak about Reality Brahman, the Brahmanas talk about the duties to be performed.
As they are terse, there arose people who explained them.
The aphorisms are the Sutras.
Those who explain them are called the Sutradhaars.
They explain the sutras and as the individuals are different , so are the interpretations.
However the essence, the core message of the Vedas are kept unchanged, certain practices vary.
Later geographical locations were taken as a Yardstick.
Read my post on Brahmins subcastes.
” During the sutra period, roughly between 1000 BC to 200 BC, Brahmins became divided into various Sakhas or branches, based on the adoption of different Vedas and different readings and interpretations of Vedas. Sects or schools for different denominations of the same Veda were formed, under the leadership of distinguished teachers among Brahmins. The teachings of these distinguished rishis are called sutras. Every Veda has its own sutras. The sutras that deal with social, moral and legal precepts are called dharma sutras, whereas those sutras that deal with ceremonials are called Srauta sutras and domestic rituals are called gruhya sutras. sutras are generally written in prose or in mixed prose and verse. These sutras are based on divine Vedas and are manmade and hence are called Smritis, meaning “recollected or remembered.”
There are several Brahmin law givers such as Angirasa, Apasthambha, Atri, Brihaspati, Boudhayana, Daksha, Gautama, Harita, Katyayana, Likhita, Manu, Parasara, Samvarta, Sankha, Satatapa, Usanasa, Vasishta, Vishnu, Vyasa, Yajnavalkya and Yama. These twenty-one rishis were the propounders of Dharma Sastras. There is a lot of contradiction among theseDarmasastas, even within one Smriti. These differences in the rules and rituals resulted in the rigid stratification of subcastes among Brahmins. None of these smritis is supreme and universally applicable throughout the Indian Continent. The oldest among these Dharma Sutras are Apasthambha, Baudhayana, Gautama and Vasishta Sutras.
Apasthambha: Apasthambha, a native of Andhra Country, belonged to Krishnayajurveda School. He belonged to fifth century BC. Apasthambha’s teachings are called Apasthambhasutra orApasthambhasmriti.
Baudhayana: Baudhayana also belonged to Krishnayajurveda School and was an inhabitant of Andhra Country. Baudhayana’s teachings are called Baudhayanasutra or Baudhayanasmriti.
Brihaspati: Brihaspati was probably the first jurist to make a clear distinction between civil and criminal justice. Yajnavalkya referred to Brihaspati. However, Brihaspati is considered to belong to 200-400 AD. Brihaspatismriti has a lot of similarities with Dhammathats of Myanmar (Burma).
Gautama: Gautama was the most ancient sage of all Brahmin lawgivers. He was quoted by Baudhayana and belonged to Samaveda School. Gautama’s teachings are called Gautamasutra orGautamasmriti.
Harita: Baudhayana and Vasishta in their Dharmasutras quote Harita. Haritasmriti or Haritasutra is an extensive work.
Katyayana: Yajnavalkya mentions Katyayana. Katyayanasmriti is quoted in several works of Viswarupa, Mitramisra etc. Smriti Chandrika cites 600 verses of Katyayanasutras. He may belong to the same period as Narada and Brihaspati.
Manu: Manu is a mythical personality and is the ancestor of the entire humankind. Manu received the code from Brahma, and communicated it to ten sages and requested Bhrigu rishi to repeat it to the other nine. This code of conduct recited by Bhrigu is called Manusmriti. For convenience, the British took Manusmriti as the paramount law of the Indian Continent.Manudharma is not only revered by Brahmins and Hindus, but also by Buddhists in Java, Siam and Myanamar. Manusmriti was composed around 200 BC, around which time a revival of Brahminism took place under the rule Sungas in the North India.
Narada: Sage Narada was probably a native of Nepal around first century AD. Naradasmriti is the first legal code unhampered by the mass of religious and moral teachings. Some authors think that Narada belonged to Gupta period when there was a distinct revival of Brahminism and Sanskrit literature.
Vasishta: Vasishta belonged to 3rd century BC and a native of North India. Vasishta’s teachings are called Vasishtasutra or Vasishtasmriti.
Vishnu: Vishnu belonged to 1st or 2nd century AD. Vishnu’s teachings are called Vishnusutra or Vishnusmriti.
Yajnavalkya: Yajnavalkya belonged to Suklayajurveda School12. He was a native of Mithila City in North Bihar and probably lived anywhere from few centuries before Christ to 200 AD. However, some scholars think he belonged to first or second century AD. Yajnavalkya Dharmasmriti has been subject of numerous commentaries. The most celebrated of all the commentaries ofYajnavlkyasmriti is Mitakshara and is practically the beginning of the Brahmin law and the so-called Hindu law. Passages from Mitakshara have been found practically in every part of the Indian Continent and became an authority. The Yajnavlkyasmriti is concise, more systematic and better arranged than the Manusmriti. From early times, commentators like Viswarupa, Vijnaneswara, Apararka, Sulapani, Mitramisra etc., from every part of India selected the Yajnavalkyasmriti as the basis of their commentaries. Passages from Yajnavalkyasmiriti appeared in Panchatantra.
Other important Brahmins who gave smritis/sutras/laws are: Angirasa, Atri, Daksha, Devala, Laugakshi, Prajapati, Pitamaha, Pulatsya, Yama, Vyasa, Samvarta and Satatapa. Prominent smriti writers of later age include, Devanabhatta or Devanandabhatta of Madras province, who belonged to ~1200 AD and wrote Smritichandrika, and Madhavacharya or Vidyaranya, who was the Prime Minister of Vijayanagara dynasty and pontiff for some time of the celebrated mutth at Sringeri in Mysore province. He wrote Parasaramadhaviya, which is a commentary onParasarasmriti.