Thomas Mars
Mars in 2013, photo by Prphotos
Birth Name: Thomas Pablo Croquet
Place of Birth: Versailles, France
Date of Birth: 21 November, 1976
Ethnicity: French, Czech
Thomas Mars is a French musician. He is the lead singer of alternative rock band Phoenix.
His father is Jean-Louis Croquet. His uncle was journalist, literary critic, novelist, and author Hellmuth Karasek; Hellmuth was born in Brno, Czechoslovakia, now Czech Republic, and later moved to Germany. Thomas is married to American director and actress Sofia Coppola, with whom he has two children.
Source: https://indiespect.ch
He is of German descent. His uncle was German literature critic Hellmuth Karasek, and this article talks about his “three German uncles” : https://indiespect.ch/2018/01/interview-phoenix-thomas-mars-en/
Karasek is a Polish surname.
While it does exist in Poland, it very much is a Czech name. I wouldn’t be surprised if the Poles with the same surname trace it back to Czechia. -ek suffix is more common in Czech last names (compared to Polish).