It was a family tradition that the Bonhoeffer children should first attend the University of Tübingen, their father’s alma mater. Their grandmother still lived there. After returning from the front, Karl-Fredrich had begun studying natural science there in 1919, and Klaus followed him for his first semester of law. During the summer semester of 1922 Sabine enjoyed staying with her grandmother. Christine was in Tübingen studying Dietrich began his theology studies. 

Eberhard BethgeDietrich Bonhoeffer: A Biography (Revised Edition); Chapter Two: Student Years: 1923-1927, 47