Siddhartha is a Brahman's son and, as such, is expected and trained to fulfill his role in the capacity of a Brahman when he becomes older. A Brahamn is a well respected role within the community following conventional precepts. However, the point of Hesse's novel is Siddhartha's rebellion against following in his father's footsteps; indeed, he wants to find his own path. Thus, he next becomes a Samana, shedding himself of all worldly goods and pleasures, and then he indulges in Samsara, the material world. Siddhartha finds Nirvana when he learns to listen to the river. If he had not left his life as a Brahman's son, he would never have found enlightenment.
I am not really sure what you are asking. If you are asking how does Siddhartha view, or feel, about the average Brahaman then the answer would be he feels skeptical. He is a member of the Brahaman culture as his father is a Brahaman. This is the highest caste in the culture from which Siddhartha is decedent. He leaves all of this behind to go find himself and Nirvana. Enotes has a very good section on Siddhartha and it can be found at the following link.