In the Vedic tradition Brahmana families are reckoned to have descended from celebrated sages of ancient times. These family lineages are referred to as gotras, of which 49 kinds are in use in India. Naturally, the present classification of the 28 nakshatras into 7 gotras is of a slightly different nature. We cannot expect all descendants of Marichi to have one of the first four asterisms as their janma nakshatra. Kalaprakashika (page 77) defines the 7 Gotras as follows:
"Divide the 28 asterisms including Abhijit into seven sets of four each. The first set (1,2,3,4) represents the Gotra of Marichi; the second set (5,6,7,8) represents Vashishtha Gotra; the third set (9,10,11,12) is Angiras Gotra; the fourth (13,14,15,16) is Atri Gotra; the fifth (17,18,19,20) is the Gotra of sage Pulastya; the sixth (21,22,23,24) is that of the sage Pulaha; the seventh (25,26,27,28) is Gutha Gotra." (4, p.77)
Note that by the insertion of Abhijit between the 21st and 22nd nakshatra (Uttarashadha and Shravana) the sequential number of Shravana and the rest has undergone a change.
Again, this classification finds a practical application in matching two birth charts for marriage compatibility. Ideally two partners should belong to different Gotras (see 4, p.77)