Mary appears to have died young, along with her son, George, but other scenarios could account for their disappearace (e.g., divorce).

Florence may have remarried after David's death, so she may not have died 1910-20, but she is not in the 1920 census as Flo/Flora/Florence HOPKINS, at least not that I can find.

I don't find a Hazel HOPKINS in the 1920 census, so she either died or married between 1910 and 1920.

1.  LDS.  Family Search: Internet Genealogy Service:  IGI - International Genealogical Index (online at FamilySearch.org).

David S. HOPKINS Spouse: Mary A. PATTERSON Marriage: 09 Dec 1858, Kalamazoo, Michigan Source: Marriage Records, 1831-1950. Kalamazoo County (Michigan). County Clerk

David S. HOPKINS Spouse: Florence E. MINICK Marriage: 22 Jul 1875, Stark, Ohio Source: Marriage Records, 1809-1916. Ohio. Probate Court (Stark County)

2.  1850 Census Every-Name-Index/Images (online at Ancestry.com):  can't find David or Mary, at least not for certain.  There is a David HOPKINS (æ 14, b. NY) living in Washington Co., NY, with his parents, Charles HOPKINS (æ 50, b. NY, wife Bety).  They are listed next to Martin HOPKINS (æ 76, b. RI, wife Phebe), who is most likely the father of Charles and, thus, grandfather of David.

3.  1860 Census Every-Name-Index/Images (online at Ancestry.com, Image #53 of 176):  Kalamazoo P.O., Village of Kalamazoo, Kalamazoo Co., MI, Roll M653_548, p. 459, PN 53, 387/384, enumerated 20 Jun 1860, official enumeration date 1 Jun 1860 (extracted by Diana Gale Matthiesen):

David S Hopkins	25	M		Carpenter Master		200	New York
May A      "	24	F					Michigan
George P   "	9/12	M					"
George Patterson	59	M		Farmer	3000	500	Pennsylvania
John McPherson	25	M		Carpenter			Canada
Betsey Waller	17	F					Ohio

4.  1870 Census Index/Images (online at Genealogy.com, Image #59-60 of 121):  Grand Rapids P.O., Grand Rapids (Ward 2), Kent Co., MI, Roll 681, pp. 286A-286B, PN 59-60, 437/430, enumerated 2 Jul 1870, official enumeration date 1 Jun 1870 (extracted by Diana Gale Matthiesen):¤

Scruby Melinda	51	F	W	Keeping House		900	Ohio
______ Emma	22	F	W				Wisconsin
______ Elizabeth	19	F	W				Wisconsin
______ George	13	M	W	At School			Wisconsin
[next page]
Hopkins David S	30	M	W	Architect		1500	New York
Hughes Edwin H	23	M	W	Ticket Agent			Michigan
Seales George	23	M	W	Printer			Michigan
Ladd John L	24	M	W	Book Keeper			New York
Fay Franklin	26	M	W	Carpenter		125	New York
Murphy William	35	M	W	Carpenter		100	New York

David should be 35, not 30.  Melinda SCRUBY's maiden name was HOPKINS, so my first thought was that David was probably her nephew, but Melinda had only two (younger) brothers, neither of whom had a son David and neither of whom was, in any case, old enough to be David's father.  I can't find a likely David among Melinda's other known kin, so their common surname may be just a coincidence and he may simply be one of her boarders.  On the other hand, 

5.  1880 Census Every-Name-Index/Images (online at Ancestry.com, Image #31 of 55):  406 Jefferson Avenue, Grand Rapids (Ward 3), Kent Co., MI, Roll T9-0588, p. 346C, PN 31, SD 2, ED 140, enumerated 11 Jun 1880, official enumeration date 1 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	10	13	24	25	26
*	406	304	347	Hopkins David S	W	M	45		/	Architect	NY	NY	NY
				_______ Florence F	W	F	30	Wife	/	Keeping House	OH	Ger	Eng
*Jefferson Ave

6.  1890 Census:  the 1890 Census Population Schedules were destroyed.

7.  1900 Census Every-Name-Index/Images (online at Ancestry.com, Image #41 of 50):  113 Paris Ave., Grand Rapids (Ward 3), Kent Co., MI, Roll T623_721, p. 329A, SN 21, SD 5, ED 54, enumerated 1 Jun 1900, official enumeration date 1 Jun 1900 (extracted by Diana Gale Matthiesen):

1900:  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

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

27

*

113

466

488

Hopkins David S

Head

W

M

Sep 1834

65

M

20

NY

RI

NY

Y

Y

Y

H

_______ Florence

Wife

W

F

Feb 1862

38

M

20

1

1

OH

Ger

OH

At School

10

Y

Y

Y

_______ Hazel M

Dau

W

F

Jul 1888

11

S

MI

NY

OH

Y

Y

Y

M?nnich Nicholus

Father in L

W

M

Dec 1821

78

Wd

Ger

Ger

Fra

1850

50

Na

Y

Y

Y

Lobdell Charles

Coachman

W

M

May 1877

23

S

MI

MI

MI

Coachman

0

Y

Y

Y

*Paris Ave

If David's father truly was born in Rhode Island, it's profoundly important for his ancestry because the Rhode Island HOPKINSes are an entirely different line from Melinda (HOPKINS) SCURBY's Massachusetts HOPKINSes, which also means their common surname is just a coincidence and he is simply boarding with her in 1870.  Florence is fibbing big time about her age, and to support her age (50, not 38), she's lied about how long she's been married (25 yrs, not 20); she's back to reality in 1910.

8.  1910 Census Index/Images (online at Ancestry.com, Image #25 of 29):  113 Paris Ave., Grand Rapids (Ward 3), Kent Co., MI, Roll T624_656 (Part 2), p. 115A, SN 12A, SD 5, ED 60, enumerated 21 Apr 1910, official enumeration date 15 Apr 1910 (extracted by Diana Gale Matthiesen):

1910:  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	7	8	9	10	11	12	13	14	17	18	23	24	25	26	27	28
*	113	216	224	Hopkins David S	Head	M	W	75	M2	35			NY	New York	NY	Eng	Own Income	Y	Y		O	F	H
				_______ Florence A?	Wife	F	W	59	M1	35	1	1	OH	Ger-German	US	Eng	None	Y	Y
				_______ Hazel M	Dau	F	W	22	S				MI	New York	OH	Eng	None	Y	Y	Y
*Paris Ave

9.  1920 Census Index/Images (online at Ancestry.com):  can't find.

10.  Anon.  1889/1900.  Grand Rapids City Directory, 1889/1900.  R.L. Polk and Co., Grand Rapids, MI (online at Ancestry.com):

Name:	David S Hopkins	David S Hopkins
Location 1:	17 Old Aldrich blk	74 Monroe
Location 2:	113 Paris avenue	113 Paris avenue
Occupation:	architect	Architect and Publisher Architectual Books
Year:	1889	1890
City:	Grand Rapids	Grand Rapids
State:	MI	MI

11.  Hackley & Hume Historic Site (online at the Muskegon County Museum web site):  our subject was apparently an architect of some note.

12.  Hume House and Hackley House (online at the Michigan Historical Markers web site).