Complex sentence: His grandfather, Boris Delaunay was a prominent Soviet mathematician, the author of the Delaunay triangulation, among his ancestors was marquis Bernard-René de Launay, the last governor of the Bastille, murdered by the attackers on that castle.
Split into simpler sentences: His grandfather, Boris Delaunay, was a prominent Soviet mathematician and creator of the Delaunay triangulation. Among his ancestors was marquis Bernard-René de Launay, the last governor of the Bastille, murdered by the attackers on that castle.