A younger son of daimyô Ii Naohide, Naonaka was declared the official heir to the household and to the domain after his elder brother Ii Naotomi died in 1787. Naonaka's other (younger) brothers included Ii Naomune and Ii Naokata. Later that year, on 1787/10/15, he had his first formal audience with the shogun, in conjunction with being officially recognized (by the shogunate) as Ii Naohide's heir.
Ii Naosuke was Naonaka's son by a secondary concubine, named Otomi no kata.
- Asao Naohiro (ed.), Fudai daimyô Ii ke no girei, Hikone Castle Museum (2004), 227.
- Asao, 228.