I feel Brahmins who have not been following Brahmin lifestyle have been there even in the past.
It is not a recent phenomenon.
I remember reading about this in the conversation between Svetaketu and Uddalaka from Chandogya Upanishad..where Uddalaka tells Svetaketu that there are no namesake Brahmanas in their lineage.
The terminology used is BrahmaBandhu(one who does not have the conduct of a Brahmana but only points to Brahmanas as his relatives)
So sir..you are right..Brahmin is a Brahmin by birth no doubt but he might be classified as a BrahmaBandhu.
I do not want to go into depth, if I am correct, this has been discussed earlier also.
Generally, Brahmana is a name generally used to denote a member of one of the four Varnas (Castes).
If one goes in detail - Brahman - refers to the Supreme Self
Brahmin or Brahmana - refers to an individual
Brahma - this refers to the creative aspects of the Universal Consciousness
Perhaps the terminology Brahmin is conceived in English from the Sanskrit termed for Brahmana.
If one goes through our earlier history, Brahmins are those who are engaged in attaining the highest
spiritual knowledge (called Brahma Vidya) through Vedic Studies and have adopted different Sakas
of Vedas. Incidentally, a question may arise, only Brahmins also should read Vedas. It is not so.
There is an exception i.e. Vishwamitra. Generally Brahmin is supposed to be thorough or well-versed
in Vedic facts and features and follow it in day to day practices too viz. Acharam, Anushtanam and
all Nithya Karma activities.
Balasubramanian
Ambattur