Ancient Sages who handed down the Vedic lore, are seven in number; Marici, Atri, Vasishtha, Angiras, Pulastya, Pulaha and Kratu. The Saptarishi (seven sages) are the seven mind born sons of Brahma. They live for a period of time known as a manvantar (306,720,000 Earth Years). During this period of time they serve as representatives of Brahma. At the end of a manvantara the universe gets destroys and Saptarishis merge in God the of filling the earth is given to new appointed Saptarishis. Saptarishis accopy a position higher than that of all other devtas. In addition to the Saptarishis, there are other classifications of Rishis. The major classifications are Brahmarishi, Maharishi and Rajarishi.
There are many list of ancient sages who are called progenitors of Gotras like Vishvamitra, Kashyapa, Gauttama, Jamadagni and Bharadvaj. This lineage (gotra) of horary sages is based on two factors; birth and learning., i.e. from father to son; and teacher (mentor - preceptor) to disciple. the 28 stars (nakshatras) including Abhijit (which is placed in Capricorn between Uttarashadha and Shravan) have been distributed among the above sages at the rate of four asterism's per sage as follows:
(1) Marichi: Aswini, Pushya (Poosam), Swati, Abhijit.
(2) Vasishta: Bharani, Ashlesha (Ayilyam), Vishakha, Sharavana (Thiruvanam).
(3) Angiras: Krittika, Magha, Anuradha (Anusham), Dhanistha (Avittam).
(4) Atri: Rohini, Purvaphalguni (Pooram), Jyestha (Kettai), Shatabhishakam (Sadhayam).
(5) Pulastya: Mrgashirsha, Uttaraphalguni (Uttaram), Mula (Moolam), Purva Bhadrapada (Pooraataadhi).
(6) Pulaha: Arudra (Thiruvaadhirai), Hasta, Purvashadha (Puradam), Uttarabhadrapada (Uttarataadhi).
(7) Kratu: Punarvasu (Punarpoosam), Chitra, Uttarashadha (Uttaraadam), Revati.
It is said that identical gotra of a boy and girl would lead to calamity. If they belong to different gotras, their union will lead to happiness, prosperity and progeny. This subject can be looked into from another angle. If the stars obtained from the longitudes of their respective lagnas belong to the same gotra or different ones, their effects would be in order moderate or excellent."
Note: This factor of compatibility of horoscopes is not taken into consideration too much these days, unfortunately with the decline in Vedic culture, and pure family lineages.
Before marriage takes place, one has to calculate whether they belong to the same family, same disciplic...... Then, if it is the same, the marriage will not take place. Same blood will not be accepted. Same family means same blood.
Consult with your family astrologer or any competent astrologer further on this Gotra agreement for your marriage before make any important decission.