[1] Bratt was born in the fishing village of Andenes on the island of Andøya in Nordland, Norway.
He was born into one of the families that constituted the remains of old Norwegian aristocracy and was elder brother of Jens Olavssøn Bratt.
He and his brother were both enrolled at the University of Cologne thanks to the sponsorship of Olav Engelbrektsson, Archbishop of Trondheim.
After the archbishop had to flee, both brothers adapted to the situation and cooperated with the new Lutheran authorities.
In his new position, he began with a transformation of the Trondheim Cathedral School to an evangelical seminary for Lutheran priests.