Born on 3rd July 1885 in Amberley, Gloucestershire, Guy Bryan-Brown was the son of the Rev. Willoughby Brown and his wife Grace. Guy was educated at St Andrew's School in Southborough before moving on to the Tonbridge School, where he was House Reposter in September 1901. He soon came up to Downing College, Cambridge, studying for the Theological Tripos, where he was the captain of the School House in 1903.

He was a keen sportsman in his younger years, serving as the captain of Downing's cricket and hockey teams, as well as the tennis club. He later secured his Blue for Hockey in 1908. By studying at Downing, he followed his elder brother Willoughby (1903) and was followed by his younger brother Douglas in 1905.

In 1906, a poem written by Guy about the family’s sporting achievements was published in The Griffin:

My brother is a batsman Whose like is seldom seen,

And often makes a mighty stand Upon our village green.

So when he played for Downing And only made a duck,

I offered him his colours To console him for his luck.

My other brother's hockey Is sight for gods and men,

And when he shoots he hits the ball Quite once in every ten.

So when one day a flying shot Bounced from his stick in goal,

The paltry gift of colours Seemed the only fitting dole.

So, when you dine with Griffins, You'll see us brothers three,

There's Old Cow, and there's Scullion, And the middle one is me.

And later on, in after life, When we have all gone down,

They'll know the use of having The glorious name of Brown.

Guy, later, moved on to Ridley Hall at Cambridge where he studied for his Honours degree in Theological studies, reading for Holy Orders and qualifying for a Teaching Diploma. Continuing his sporting endeavours, he represented his college in both the rugby and football associations. In 1908 he was appointed to a Mastership at Trinity College, Glenalmond, and was ordained in 1909 before proceeding in 1913 to Christ’s College, Christchurch, Canterbury, New Zealand, as Chaplain-Master. There he continued his sporting interests, including representing Canterbury in cricket.

In 1913 the, now, Reverend Bryan-Brown became Chaplain to Christ’s College Cadet Corps, and Chaplain to the Forces (4th Class) with the New Zealand Chaplains Department in March 1914. In the Christmas holidays of 1916-17 he was at Trentham Training Camp and was assigned as Temporary Army Chaplain (and Captain) with the 21st New Zealand Expeditionary Force 21st Reinforcements and later with the 3rd Canterbury Battalion.

Originally, Guy declined the position but reapplied in January 1917. He sailed to England on 14th February 1917 as a temporary chaplain with the 21st Reinforcements and served with the Expeditionary force from 29th May onwards.

On 4th October 1917, he was killed in action at an aid post near Ypres, during the ANZAC advance towards Passchendaele. A Staff Captain wrote that: "The doctors who were with him say that he rendered invaluable assistance during the day in bringing in and dressing the wounded, and I am sure, from what I know of him, that he never spared himself or thought for one moment of the risk he was running, so long as he could help those who were in need”.

There are various reports surrounding the circumstances of his death. However, a fellow Chaplain stated that he was "bust blocking up a window of a dressing station from the outside, when three shells came in quick succession. I saw him fall staggering sideways, and I rushed to him at once, but he was dead… If ever a man gave his life away for others, that man was G. Bryan-Brown".

Guy is commemorated today on the Tyne Cot Memorial, N.Z. Apse, Panel 9.