Aleksander Ratz was born in 1946 in Krakow as the son of Emilia (née Endler) and Marcin (Martin) Ratz. His mother came from Warsaw and his father came from Vienna. After the outbreak of World War II, Aleksander Ratz's parents fled to the east. They spent the war in the Soviet Union, where they completed their electromechanical studies.

After the war they settled in Krakow. In 1949 they moved to Warsaw and lived at Olimpijska Street in Mokotów. His father worked in the heat and power plant in Żerań, and his mother in the Planning Commission.

Alexander Ratz was active in scouting, he was a student of the Reytan Secondary School. He took up studies at the Faculty of Mechanical Engineering and Technology of the University of Warsaw.

As a result of the events of March 1968, his parents were made redundant and decided to leave Poland. Aleksander Ratz, together with his younger sister and father, left for Vienna. After two weeks, Aleksander Ratz moved to Sweden, where he did not have to start his studies from the beginning - in 1968 he was in his fifth year of studies at the Warsaw University of Technology. He received his Master's degree in engineering in 1971.

In 1970 his fiancée, Tola, joined him in Sweden.

His mother left Poland in 1972, earlier her applications for permission to leave were repeatedly rejected. Tola and Aleksander Ratz live in Stockholm and have three sons and seven grandchildren.