He should be on the 1930 and 1940 census.
There were a few John Miller's listed in census
Not sure if this is who your looking for.
Good luck in your search

1940 census
Name: Ralph Miller Junior
Age: 18
Estimated Birth Year: abt 1922
Gender: Male
Race: Part-Hawaiian (Hawaiian)
Birthplace: Hawaii
Marital Status: Single
Relation to Head of House: Son
Street: Naio Street
Sheet Number: 15B
father: Ralph age 40 Bn 1900 Minnesota (works at army depot)
mother: Phoebe 37 1903 Hawaii (part Hawaiian)
children Part - Hawaiian
Ralph 18
Ellen 17
Amy 16
Gertrude 15
Walter 13
Marjorie 12
Source Citation: Year: 1940; Census Place: Honolulu, Honolulu, Hawaii; Roll: T627_4587; Page: 15B; Enumeration District: 2-143.