Welter was born on 25 February 1916 in Cologne-Lindenthal. He was the son of merchant Julius Welter and his wife Gertrud, née Morian. On 29 February, he was baptised into the Catholic Church with the full name of Kurt Johann Franz Ludwig Welter. The family moved to Brühl where Welter Volksschule on 1 April 1922. On 1 April 1929, he transferred to the boys school St. Antonius in Aachen, graduating from this school on 1 April 1930. On 1 May 1930, Welter attended the private Rohloff merchant school (see August Rackow) in Cologne from which he graduated on 31 March 1931. In parallel, he worked in his father's company.
