Lord Brahma is the first of 3 major Hindu gods called the “Trimurti,” which includes Brahma, the creator, Vishnu, the preserver, and Shiva, the destroyer. Lord Brahma is born from the union of Brahm-Kaal & Durga or Kaali (Maya/Ashtangi/Prakriti Devi).
Saptarishis were the mind born sons of Brahma. They were advised to perform procreation. Blood
relation was not a criterion for the creation. Similarly age difference too was not seen.
In the First Manvanthara the Saptharishies were
a) Mareechi (Marichi) b) Atri c) Angeerasa (Angirasa) d) Pulasthya e)
Pulaha f) Kratu and g) Vasistha.
Other than Saptarishi's Brahma had other mind born sons like Manu, Brighu and Narada.
His Mind born daughter was Satrupa or Satarupa.
Manu mind born son of Brahma married Satrupa mind born
daughter. They Gave birth to a lot of children and grand children.