Marion was born on his family’s farm in Petite-Hour, Houyet, Belgium on 10 October 1893. He was the youngest of five children – and the only son – born to Henri Joseph Marion and Léonie Adèle Joseph Baudry. At the age of 12, he started helping his parents with farm work.
Marion avoided the draft during World War I, but still had to do military service in Sint-Truiden, a city in Belgian Limburg. After completion, he returned to the family farm and never relocated, working as a farmer. His mother was widowed during this time.
On 19 May 1926, aged 32, Marion married Céline Joséphine Ghislaine Nénène Lotin, who was 11 years his junior. The couple had seven children. Marion continued to work in the stables as a nonagenarian, with his son Norbert and daughter Marie-Louise taking over the running of the farm. His wife died in 1991 at the age of 87.
In 1975, Marion suffered third-degree burns during a brush fire on his farm. He attended church several times a week, and watched the news every day; he liked to keep abreast of political affairs. He smoked his pipe twice daily until his death.
At the age of 105, Marion became the oldest living man in Belgium following the 13 March 1999 death of Paul Henrard. He surpassed the age of Clement De Vos in September 2002 to become Belgium’s oldest man ever (apart from Jan Reyskens, a Belgian-born supercentenarian who died in the Netherlands). He recovered from pneumonia aged 109.
Marion became Belgium’s oldest resident upon the death of Anne Vandermersch-Adam, two days before his 110th birthday. He died on 28 December 2003 at the age of 110 years, 79 days, in the same farmhouse that he was born in. He was succeeded as Belgium’s oldest living person and man by 108-year-old Victoire Ricaille and 104-year-old Georges Nevejans respectively. He was survived by 18 grandchildren and 38 great-grandchildren.