Complex sentence: His paternal grandfather was editor-in-chief in a Catholic republican newspaper in Spain and had to hide persecuted priests in his house during the Spanish Civil War due to persecutions by trotskyists and anarchists.
Split into simpler sentences: His paternal grandfather was editor-in-chief at a Catholic republican newspaper in Spain. He sheltered persecuted priests in his house during the Spanish Civil War due to persecutions by trotskyists and anarchists.