He was the eldest of three brothers: Sebastian (1921–1945), the historian Karl Otmar (1923–2014), and the Jesuit Richard Freiherr von Aretin (1926–2006).
In spring of 1947 he, alongside Anton Donhauser and other members and functionaries, left the CSU for the Bavaria Party.
This was due to disappointment with the Schäffer-Hundhammer-wing of the CSU not having been able to implement enough policies focused upon Bavaria-centric issues.
From 1949 until 1953 von Aretin was a member of the German Parliament, in which he represented the Bayern Party.
He was later a member of the Landtag of Bavaria from 1950 until 2 May 1951, in which he represented the locality of Vilshofen an der Donau.