Harvey Brown appears to be an 21/22 y/o from Lee twsp, Platte County Missouri, single. His brother marries and names their first male James(father's name) and their second Harvey born in 1865.

1860 Census
Name: Harvey Brown
Age: 18
Birth Year: abt 1842
Gender: Male
Race: White
Birth Place: Missouri
Home in 1860: Lee, Platte, Missouri
Post Office: Platte City
Dwelling Number: 889
Family Number: 878
Married Within Year: Y
Attended School: Y
Household Members Age
Jas S Brown
58
Rebecca Brown
47
Andrew S Brown
27
Harvey Brown 18
Jane L Brown
14
Cynthia C Brown
11
Jas Brown
8
Sarah J Brown
19
Margaret A Brown
2
Mary C Brown
6/12
Jacob W Brown
22

He also has a draft record 1863
Name: Harvey Brown
Birth Year: abt 1842
Place of Birth: Missouri
Age on 1 July 1863: 21
Race: White
Marital Status: Unmarried (Single)
Residence: Lee, Platte, Missouri
Congressional District: 6th
Class: 1

He is in the same household and location in 1850
Name: Harvey Brown
Gender: Male
Race: White
Age: 9
Birth Year: abt 1841
Birthplace: Missouri
Home in 1850: Lee, Platte, Missouri, USA
Line Number: 42
Dwelling Number: 231
Family Number: 231
Household Members Age
James Brown
47
Rebecca Brown
37
Andrew Brown
16
Margaret Brown
15
Jacob Brown
13
Harvey Brown 9
Jame Brown
5
Cynthia Brown
1
Jane Brown
83