H.G. Gabriel Mar Gregorios was born on January 28, 1948 as third son of Thumpamon Vadakke Thazhethil, Kanjikkal Chacko John and Pandalam Kudassinadu Ramanattu Mulamoottil Aleyamma John and the family belong to the Kudassinadu St. Stephens Cathedral of Chengannoor Diocese. Preliminary education of Gabriel was done at St. Stephens High School, Pathanapuram and Pre-Degree in the St. Stephens College. After graduating in English Literature [B.A.] from Basalios College, Kottayam, Gabriel proceeded for Theological studies at Orthodox Seminary, Kottayam. He had Acquired GST from there and B.D. degree from Serampore University.

On November 4, 1969 Gabriel was ordained as deacon and on February 8, 1974, as a priest. Fr. Gabriel took M.T.H degree in New Testament, Three year Diploma in Hebrew Language and two year Diploma in Aramaic Language and great proficiency in Greek from the Paris Catholic University. He had done research in Lutheran School of Theology in Chicago, USA, about 'Grace in the Epistles of St.Paul'. Based on the dissertation and Thesis of this research study, he was awarded doctorate by the Serampore University. Also he had undergone post graduate research in Cambridge University. Fr. Gabriel had acquired proficiency in ancient languages of Aramaic, Hebrew, Greek, Syriac and in modern languages German, French and English etc.

Fr. Gabriel served as vicar of fifteen parishes including parishes at Bombay, Delhi, Kottayam, Trivandrum over period of long 30 years. He was deeply involved in many ecumenical corporate activities of the Church. He had also served as Registrar and Director of F.F.R.R.C which act as a United Theological research Centre of Marthoma, C.S.I, Orthodox Seminaries [1995-2003]. He had a major contribution to uplift this centre as one of the biggest Theological Research Center where maximum number of researchers got attracted from different states of India. He is the chief architect of this institution to elevate it as Doctoral Research Center giving M.T.H degree in 8 subjects from 1999 onwards. Fr. Gabriel also acted as Malankara Orthodox Church representative of ecumenical organizations like Orthodox-Marthoma Dialogue Forum, Orthodox-Lutheran Dialog Forum, Bible Society Kerala Auxiliary Committee, Theological Literature Forum etc. for six years each.

During 1996-2000 he was the treasurer of Society for Biblical Studies which is an organization of the Theological Scholars in India. He also held the posts of Associate Director of the Orthodox Youth Magazine, Organizer of the publication of the Sunday Schools books for Oriental Orthodox Churches, Convener of the Golden Jubilee Celebrations of Vattasseril Mar Dionasios [1983-85], Orthodox Seminary Regustrar, Warden and Alumni Association President.

From 1982 onwards Fr. Gabriel is the Professor of New Testament Department in Orthodox Theological Seminary, Kottayam. He also holds the post of Fellow of George Bell Ecumenical Institute, England, and Administrative Committee Member of Serampore University etc. He had also authored many Theological Books like Towards A New Humanity, Towards The Grace Of God, Cross And Grace etc. On August 7, 2004 Fr. Gabriel was elevated as Ramban by Basalios Mar Thoma Mathews II at Devalokam Catholicate Aramana Chapel.

H.G. Mar Gregorios authored more than 100 books in English and Malayalam. Some of his distinguished works are Towards the Grace of God, Towards a New Humanity, Cross and Grace, Gurumukhathu Ninnum[Part I & II] Athmeeyathyude Yadartha Shrothassukal.