Complex sentence: Also present was Agrippina the Younger with her son, Lucius Domitius Ahenobarbus (Nero), who received greater acclamation from the audience than did Messalina and Britannicus.
Split into simpler sentences: Also present was Agrippina the Younger with her son, Lucius Domitius Ahenobarbus (Nero). Agrippina and Nero received a greater acclamation from the audience than did Messalina and Britannicus.