1.  Marriage Record:

2.  1880 Census Images (online at Ancestry.com; Image #43 of 68):  Kickapoo Twp., Leavenworth Co., KS, p. 35A/C, PN 43, SD 3, ED 143, enumerated 24 Jun 1880 (extracted by Diana Gale Matthiesen):

1880:  for an explanation of the column headings, please see What the Numbers in the Federal Census Mean (missing columns contained no data).

1

2

3

4

5

6

8

9

10

13

24

25

26

271

285

McGraw William

W

M

42

/

Farmer

Ireland

Ireland

Ireland

______ Mary A

W

F

21

Wife

/

Keeping house

Kansas

Ireland

Ireland

______ Mary J

W

F

5

Daughter

/

Kansas

Ireland

Kansas

______ Henry

W

M

3

Son

/

Kansas

Ireland

Kansas

______ Andrew

W

M

1

Son

/

Kansas

Ireland

Kansas

______ Samuel

W

M

28

Brother

/

Kentucky

Va

Ky

272

286

Ward, Perry

W

M

58

/

Farmer

Kentucky

Va

Ky

[Perry's wife and children]

Perry WARD is not related; I include the beginning line of his record as evidence for the source of the error in Samuel's birthplace and the birthplaces of Samuel's parents.  Samuel cannot be William's brother unless their parents were born in the same places!  It's obvious that the enumerator, in transcribing his field notes into the schedule, made a mistake and gave Samuel the birthplaces of the next individual.  For whatever reason, he is also ten years off on Samuel's age.

4.  1890 Census:  the 1890 census population schedules were destroyed.

5.  1900 Census Index/Microfilm (online at Genealogy.com):  by this time, William is deceased and Mary has remarried, to James Henry DAILEY; and they should be living in Kansas City, KS.  I can't find James DAILEY, nor can I find any of the children under the surname McGRAW.