All Brahmanas in this world are Brahmanas on account of conduct. A Shudra, if he is of good conduct, is considered as equal to a B-ahmana.
सर्वोऽयं ब्राह्मणौ लोके वृत्तेन तु विधीयते। वृत्ते स्थितस्तु शूद्रोऽपि ब्राह्मणत्वं नियच्छति॥