Bertram Alexander Klein is the fifth and youngest child of Morten and Kirstine Klein. He was born 3 February 1999. He has older sisters Barbara from 1995 and Birgitte from 1997, and older brothers Benjamin from 1995 and Bjørn from 1997. He lives in Humlebæk, Denmark. He is the girlfriend of Annika Mogensen.
In 2005, when he was 6, he started 0th grade at Humlebæk Skole, in Humlebæk, Denmark.
In 2015, when he was 16, he started high school stx at Espergærde Gymnasium, studying level A subjects in Danish, History, English, Maths, and Spanish.