The same family is listed twice on 1880 Census with slight name variations:

Name: Victor Bartels
Residence: Sacramento, Sacramento, California
Birthdate: 1875
Birthplace: California, United States
Relationship to Head: Son
Spouse's Name:
Spouse's Birthplace:
Father's Name: Wm. Bartels
Father's Birthplace: Germany
Mother's Name: Harriet Bartels
Mother's Birthplace: Germany
Race or Color (Expanded): White
Ethnicity (Standardized): American
Gender: Male
Martial Status: Single
Age (Expanded): 5 years
Occupation:
NARA Film Number: T9-0071
Page: 101
Page Character: A
Entry Number: 2991
Film number: 1254071
Household Gender Age
Parent Wm. Bartels M 38
Parent Harriet Bartels F 25
Willem Bartels Jr. M 7
Victor Bartels M 5
Kittie Bartels F 2

----
Name: Victor Bartels
Residence: Sacramento, Sacramento, California
Birthdate: 1875
Birthplace: California, United States
Relationship to Head: Son
Spouse's Name:
Spouse's Birthplace:
Father's Name: Wm. Bartels
Father's Birthplace: Germany
Mother's Name: Harriet Bartels
Mother's Birthplace: Germany
Race or Color (Expanded): White
Ethnicity (Standardized): American
Gender: Male
Martial Status: Single
Age (Expanded): 5 years
Occupation:
NARA Film Number: T9-0071
Page: 101
Page Character: A
Entry Number: 2991
Film number: 1254071
Household Gender Age
Parent Wm. Bartels M 38
Parent Harriet Bartels F 25
Willem Bartels Jr. M 7
Victor Bartels M 5
Kittie Bartels F 2
=========================

1900 Census (Willem Sr. has died - and one infant death is recorded)

Name: Henrietta Bartels
Titles:
Residence: Sutter Township, Oak Park Precincts 2 and 2 1/2, Sacramento, California
Birth Date: Jan 1855
Birthplace: Pennsylvania
Relationship to Head-of-Household: Self
Spouse Name:
Spouse Titles:
Spouse Birth Place:
Father Name:
Father Titles:
Father Birthplace: Germany
Mother Name:
Mother Titles:
Mother Birthplace: Germany
Race or Color (expanded): White
Head-of-household Name:
Gender: Female
Marital Status: Widowed
Years Married:
Estimated Marriage Year:
Mother How Many Children: 6
Number Living Children: 5
Immigration Year:
Enumeration District: 0097
Sheet Number and Letter: 9A
Household ID: 197
Reference Number: 36
GSU Film Number: 1240099
Image Number: 00073
Household Gender Age
Henrietta Bartels F
Child William F L Bartels M
Child Victor J Bartels M
Child Katherine E Bartels F
Child John C Bartels M
Child Ruby E Bartels F

-----------------------------------------

1920:

Name: Henrietta Bartels
Residence: Township E Gravelly Valley Bartlett Precinct, Lake, California
Estimated Birth Year: 1857
Age: 63
Birthplace: Pennsylvania
Relationship to Head of Household: Mother
Gender: Female
Race: White
Marital Status: Widowed
Father's Birthplace:
Mother's Birthplace:
Film Number: 1820101
Digital Folder Number: 4293701
Image Number: 00605
Sheet Number: 1
Household Gender Age
Child Victor J Bartels M 42y
Henrietta Bartels F 63y
Annie E Gregory F 65y
Elmer F Hildreth M 34y

In addition to listings on prior censuses with family, this may be a match for 1920:

Name: Katie Bartles
Residence: Precinct 1 Assembly District 30 San Francisco City, San Francisco, California
Estimated Birth Year: 1877
Age: 43
Birthplace: California
Relationship to Head of Household: Self
Gender: Female
Race: White
Marital Status: Single
Father's Birthplace:
Mother's Birthplace:
Film Number: 1820138
Digital Folder Number: 4293844
Image Number: 00703
Sheet Number: 6

Name: John C Bartels
Birthplace: California
Relationship to Head of Household: Self
Residence: Township 3, Lake, California
Marital Status: Single
Race : White
Gender: Male
Immigration Year:
Father's Birthplace: Germany
Mother's Birthplace: Pennsylvania
Family Number: 21
Page Number: 3
Household Gender Age
John C Bartels M 26y
Ruby Bartels F 17y (sister)
Victor J Bartels M 32y (brother)