Many pre-Columbian societies, such as the Inca and Aztec, utilized marriage as a tool for diplomacy and cementing control between noble families.
While the book by Charles C. Mann is a non-fiction historical work and does not contain romantic storylines or fictional relationships, its detailed account of pre-Columbian civilizations offers a rich foundation for understanding real-world social and political structures of that era.
Characters frequently struggle between their personal affections and their responsibilities to their tribe, empire, or family traditions. Romantic Tropes in Historical Settings 7 Female Love Interests | Author J.S. Morin
If you are looking for romance and relationship dynamics set in or inspired by this historical period, Common Relationship Dynamics