Constantine's father Christos, from the island of Imbros island on the Aegean, first traveled to Khartoum, a regional trade centre in Sudan, in the southern Sahara, to make his mark. There he heard about the vast discoveries of gold and opportunities in South Africa. The lure of the new El Dorado sparked the world’s largest gold rush. It drew a large influx of foreigners from around the globe in search of fortune, who were enticed by feverish dreams of great wealth and opportunity. In 1905, he took off and traveled steerage to South Africa to seek his fortune in the burgeoning gold-mining town of Germiston, South Africa. He returned financially established to Imbros in 1912, to find a bride and married a young Eleni. During the First Balkan War in 1913, when Turkey took control of the Imbros, most of the island’s Greek-speaking Orthodox Christians fled. Christos left with his pregnant wife, brothers, extended family and settled in Germiston, South Africa. Constantine, the son of Christos and Eleni, the second youngest of six children, was born on November 1, 1920, in South Africa. They affectionately called him by his nickname, Cossie. In South Africa, the ‘Corner Café’, typified the early Greek and Cypriot immigrants, they worked long, hard hours behind the till staying open for extended hours. These new immigrants saw the cafés as a stepping stone towards a better financial position and a better life for themselves and their families. Most of them were invited to South Africa by relatives and fellow countrymen. The early Greeks described this influx phenomenon as ‘chain immigration. When an immigrant arrived in the new country, he typically worked as a ‘μπακαλόγατος’ bakalogatos, a counter assistant, to gain the experience necessary to earn, save, in time open his own business. In time, he required assistance in his business and invited relatives from Greece to join him, thus continuing the chain of immigration. The long hours and hardships in the cafés prevented these entrepreneurs from having any social life. Even worse for the Greek immigrant retailers, they were often subjected to periodic outbursts of verbal and physical abuse arising out of xenophobia. Christos and Eleni Christelis toiled away behind the counter of Olympia, the first corner café in Georgetown, Germiston, in the heart of the Rand goldfields. Christos also owned three racehorses at Gosforth Park Race Club, a major horse racing facility, in the Transvaal, he died in 1936. The whole Christelis clan did well, they became property owners and contributed to the development of the Greek community in Germiston.

From a young age, Cossie was raised in the Greek Orthodox faith, serving as an altar boy. He attended Germiston High School, an English-medium government school established in Germiston in September 1917 with the school motto “Scientia et Humanitas”, Science and Culture. He played sport at school and loved the game of rugby. The school once enjoyed the reputation of being regarded as having the best schoolboy rugby team in the region. He also took part in the school cadet detachment, a discipline to learn military obedience. Cadets spent time during extra periods or after school marching and playing instruments in a marching band with drums, cymbals, and valveless bugles. There was also rifle shooting training, using .22 caliber rifles. Uniforms consisted of caps, khaki-colored short pants, and shirts with epaulets, long khaki knee socks, and brown boots. It exposed Constantine to leadership, responsibility, and cooperation at a young age. Just to the north of the school is Victoria Lake, better known today as Germiston Lake. It is manmade and was once used by the local gold mines, bordered by industry in the North, a park, and Germiston Boys High School on the Rand Airport Road in the South. The Germiston High School Rowing Club, of which Constantine was a member, is based at the lake and is one of the oldest rowing clubs in South Africa. A spirit of perseverance ran through the club, which resulted in some outstanding results at regattas in which he competed. The nearby aerodrome, Rand Airport, was officially opened on December 21, 1931. The airport was one of the first in Johannesburg and initially serviced its mining and manufacturing industries. Rand Refinery, the largest integrated single-site precious metals refining and smelting complex in the world used to export its refined gold by air. In early 1939, the Union Defence Force took control of Rand Airport and established training schools there to train pilots for the war effort. The plane was widely produced and used primarily for training by most Commonwealth aircrew during the Second World War. While Cossie was in his last year of school, he heard the loud roaring radial engine Harvard’s trainers rumble overhead. Their propeller tips rotated so fast they broke the sound barrier. When the Harvard’s took off, hearing that amazing throaty growl overhead kindled Constantine’s passion for aviation.