Complex sentence: His mother's family originated from Mexico City, his grandfather a French-Indian "mestizo", his great grandfather had immigrated to Mexico in the 1820s shortly after the country's independence from Spain and married a woman who was half Aztec.
Split into simpler sentences: His mother's family originated from Mexico City, his grandfather a French-Indian "mestizo". His great grandfather had immigrated to Mexico in the 1820s shortly after the country's independence from Spain and married a woman who was half Aztec.