Complex sentence: As an adult he had family connections to Molanus, a religious reformer who would later have to flee Louvain, and a close friend and correspondent, Philip Melanchthon, one of the principal Lutheran reformers.
Split into simpler sentences: As an adult Mercator had family connections to Molanus, a religious reformer who would later have to flee Louvain. Also he was a close friend and correspondent of Philip Melanchthon, one of the principal Lutheran reformers.