Civil was born in the 12th arrondissement of Paris on 29 January 1990, to a French mother from Avignon and a Tahitian father. His parents are both University professors of Spanish. His paternal grandmother is Tahitian and his paternal grandfather is Catalan. He has an older sister.
In addition to his native French, Civil also speaks English, Spanish, and a bit of Italian.
Civil has a depigmentation of the skin of his arms and a lock of white hair since he was fifteen. He told French magazine Paris Match in 2019 that no doctor could tell him why, but he believes this happened due to stress.
Civil started acting at the age of fourteen. He signed up for an acting class because he wanted to get closer to a girl who was taking acting lessons. The feeling was not mutual, but he ended up falling in love with theater. After spotting him at a school play, the mother of one of the students who was also a casting director encouraged him to continue on this path and insisted that he should go to auditions. Thanks to her, he passed a test and landed a role in his first film, Le Cactus. In 2006, he made a brief stint at the French drama school Cours Florent, which he did not like.
