Complex sentence: Cornides was a member of the Oldenbourg family, owners of "R. Oldenbourg Verlag" publishers; a German publishing house founded in 1858 by Rudolf Oldenbourg.
Split into simpler sentences: Cornides was a member of the Oldenbourg family, owners of "R. Oldenbourg Verlag" (publishers). A German publishing house started in 1858 by Rudolf Oldenbourg.