From Brahma all the seven great sages, and before them four other great sages, named Sanaka, Sananda, Sanatana, and Sanatkumara, and the fourteen Manus, are manifest. BG 1972 purports
Bhagavad-gita As It Is
BG Chapters 7 - 12
The seven great sages and before them the four other great sages and the Manus [progenitors of mankind] are born out of My mind, and all creatures in these planets descend from them.
The Lord is giving a genealogical synopsis of the universal population. Brahmā is the original creature born out of the energy of the Supreme Lord known as Hiraṇyagarbha. And from Brahmā all the seven great sages, and before them four other great sages, named Sanaka, Sananda, Sanātana, and Sanatkumāra, and the fourteen Manus, are manifest. All these twenty-five great sages are known as the patriarchs of the living entities all over the universe. There are innumerable universes and innumerable planets within each universe, and each planet is full of population of different varieties. All of them are born of these twenty-five patriarchs. Brahmā underwent penance for one thousand years of the demigods before he realized by the grace of Kṛṣṇa how to create. Then from Brahmā, Sanaka, Sananda, Sanātana, and Sanatkumāra came out, then Rudra, and then the seven sages, and in this way all the brāhmaṇas and kṣatriyas are born out of the energy of the Supreme Personality of Godhead. Brahmā is known as pitāmaha, the grandfather, and Kṛṣṇa is known as the prapitā-maha, the father of the grandfather. That is stated in the Eleventh Chapter of the Bhagavad-gītā. (BG 11.39).