Brahmarshi Vashishth is one of the 10 Maanas Putra (mental son) of Brahmaa Jee - others are Mareechi, Atri, Angiraa, Pulastya, Pulah, Kratu, Bhrigu, Daksh and the tenth one is Naarad. Brahmaa Jee appointed him as the Purohit of Soorya Vansh kings. Being Purohit of a family is not good for a higher Rishi, so Vashishth Jee didn't want to accept that job, but Brahmaa Jee explained him that he will greatly be benefited by this job, as later Vishnu's incarnation is going to appear in this family and he would have the opportunity to live with Bhagavaan Himself. Hearing this Vashishth Jee got happy and he accepted this job. Later Raam was born in this Vansh and Vashishth had all kinds of opportunities with Him.

Once Vashishth Jee showed his Yog power to the King Vishwaamitra, so Vishwaamitra also tried to be a Brahmarshi and became Brahmarshi from Kshatriya after a long Tapasyaa.

Once the eight Vasu came to see Vashishth Jee along with their wives and saw Nandinee cow with him. One of the Vasu's wife got attracted to that cow, so that Vasu stole that cow from there to please his wife. When Vashishth Jee came to know about this, he cursed all the Vasu to be born on Prithvi. On request to Gangaa, she bore them and gave all of them Mukti except the one who stole the cow. (read further in Shaantanu)