Another political form which Europeans found unusual was the existence of paired identities within a single polity. Most often - though it was by no means a widespread phenomenon - two royal or quasi-royal families held interlinked authority, often describing their relationship as one between elder and younger brother, with all the attendant complications of affection and rivalry, or between upstream and downstream. The kingdoms of Jambi and Palembang had one such role; more intricately related were the two royal families, one Batak and one Malay, in the northern Sumatran state of Barus.
Andaya, Barbara Watson, To live as brothers: southeast Sumatra in the seventeenth and eighteenth centuries. Honolulu: University of Hawaii Press, 1993.
Borschberg, Peter, ‘Luso-Johor-Dutch relations in the Straits of Malacca and Singapore, c. 1600-1623', Itinerario 28, no.2 (2004), pp. 15-43.
Drakard, Jane, A Malay frontier: unity and duality in a Sumatran kingdom. Ithaca, NY: Cornell University Southeast Asia Program, 1990.
Drakard, Jane, A kingdom of words: language and power in Sumatra. New York: Oxford University Press, 1999.
Lombard, Denys, Le Sultanat d'Atjéh au temps d'Iskandar Muda, 1607-1636 Paris: École Française d'Extrême-Orient,1967.
Reid, Anthony, Southeast Asia in the Age of Commerce 1450-1680, volume two: expansion and crisis. New Haven: Yale University Press, 1993.
Map number from Cribb, Historical Atlas of Indonesia (2000)
Aceh, Aru, Ayutthaya, Bangka, Banten, Barus, Batavia, Bengkulu, Deli, Indragiri, Indrapura, Jambi, Johor, Kedah, Lampung, Lingga, Malay Peninsula, Mataram, Melaka, Nias, Pagarruyung, Pahang, Palembang, Panai, Pariaman, Perak, Perlis, Rokan, Siak, Singkel, Sumatra, Tiku