The son of an Italian immigrant from Piedmont,[1] Forni was born in Belfort, in 1941.

At 17, he had to stop studying, and he started to work as an unskilled worker in Peugeot factories.

He finally graduated from high school at 21 and started law studies at the University of Strasbourg.

[citation needed] Member of the Socialist Party, his political career started in 1971 when he became municipal council.

He was awarded Grand Cross of the Order of Merit of the Republic of Poland (2000).