Every Brahmin is a descendant of sages, which is why every Gotra or clan of Brahmins has an associated list of Pravaras, a list of the sages they're descended from. For instance, I am a Brahmana belonging to Vadhula Gotra, and my Pravaras are "Bhargava, Vaitahavya, Savedasa", which means that I am descended from the sages Bhrigu, Vitahavya (whom I discuss here), and Savedasa. In any case, I was looking at Wikipedia’s list of Pravaras for various Gotra, when I came across the following Pravaras for Bhargava Gotra:
For those who don't know, Tvashta, also known as Vishwakarma, is the architect of the gods. As I discuss in this question, he built Indra's city of Amaravati, Ravana's city of Lanka, and Krishna's city of Dwaraka, and he once caused the Earth to submerge! And Vishvaroopa, also known as Trisiras was the three-headed son of Tvashta, As I discuss here, Indra killed Trisiras, and to take revenge Tvashta created a demon called Vritrasura to kill Indra. Indra ultimately killed Vritrasura, and it is this deed that Indra was most famous for in ancient times.
But my question is, why would Tvashta and Trisiras be listed in the Pravaras for Bhargava Gotra? That means that Brahmins belonging to Bhargava Gotra are descended from them. But Bhargava means descendant of Bhrigu, and Tvashta isn't a descendant of Bhrig at all; he's one of the Adityas or sons of Kashyapa and Aditi, as described in this chapter of the Srimad Bhagavatam:
The names of the sons of Aditi are as follows: Vivasvān, Aryamā, Pūṣā, Tvaṣṭā, Savitā, Bhaga, Dhātā, Vidhātā, Varuṇa, Mitra, Śatru and Urukrama.... Racanā, the daughter of the Daityas, became the wife of Prajāpati Tvaṣṭā. By his semen he begot in her womb two very powerful sons named Sanniveśa and Viśvarūpa.
Thus Tvashta would be classified as a Kashyapa, not a Bhargava. So why would he be listed in the Pravaras for Bhargava Gotra?
Note that in this question, I discuss a community of metalworkers and craftsmen who are considered low-caste by many people, but who claim to be Brahmanas descended from Vishwakarma. But they're claims are considered unfounded, whereas Bhargava Gotra is a well-established Brahmana Gotra. So I'm not sure if there's a connection. Also, there is of course the possibility that Wikipedia has incorrect information, so does anyone know whether this set of Pravaras is mentioned in Hindu scripture?
EDIT: This excerpt from the Upodhgata Pada of the Brahmanda Purana says that Tvashta and Trisiras are the son and grandson of Bhrigu's son Sukracharya, guru of the Asuras:
The mental daughter of the Manes named Somapas (imbibers of the Soma juice) was well-known by the name of Gau. She became the wife of Shukra and gave birth to his four sons. They were Tvashtar, Varatrin, Shanda, and Marka.... Trishiras alias Vishvarupa was the great (elder) son of Tvashtar. He was born of Yashodhara, daughter of Virochana. He became very famous.
How can this be reconciled with the statements that Tvashta one of the twelve sons of Kashyapa and Aditi? Was he initially born as the son of Kashyapa and then reborn as the son of Sukracharya or vice versa? Are there any scriptures that discuss this?