Complex sentence: Many prominent "mestizo de sangley" families belonging to this landlord class acquired vast landholdings during this period; their holdings were second to those of the Catholic religious orders, who owned the most land in the Philippines.
Split into simpler sentences: Many prominent "mestizo de sangley" families belonging to the landlord class acquired vast landholdings during this period. Their holdings were second only to those of the Catholic religious orders, who owned the most land in the Philippines.