— born in Sunbury, Northumberland Co., PA:
2.  Bertha STRAUB, b. Oct 1881
3.  Minnie Alice STRAUB, b. 8 Jan 1885 
4.  Ralph Rupert STRAUB, b. 18 Sep 1885
5.  Eva B. STRAUB, b. 1889
6.  Nora M. STRAUB, b. Jul 1893
7.  Tillman "Till" STRAUB, b. ca. 1895; died young
8.  Lillian STRAUB, b. ca. 1897; died young

In the 1900 census, Phoebe states she's had eight children with six surviving, which jibes with the above list.  But in the 1910 census, Phoebe states she's had nine children with seven surviving.  Who's the seventh?  About the only way they could have had a child who completely missed the censuses is if they had a daughter born ca. 1882/3 who married before 1900.
Phoebe had two children (Minnie and Ralph) just nine months and ten days apart?!

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

John A. STRAUB Birth: Jun 1857, Snyder, Pennsylvania; Death: 15 Nov 1915 Father: Edward STRAUB; Mother: Elizabeth Source: patron submission

John A. STRAUB Death: 15 Nov 1915 Marriage: 12 Jan 1885, Sunbury, Northumberland, Pennsylvania Spouse: Phoebe Anne STEPP Source: patron submission

1b.  LDS.  Family Search: Internet Genealogy Service:  AF - Ancestral File (online at FamilySearch.org).

John S. STRAUB Birth: Jan 1856, Snyder, Pa Father: Edward STRAUB; Mother: Elizabeth Marriage: 1878, Sunbury, Northumberland, Pa Spouse: Phoebe Anne STEPP Birth: 23 Jul 1856, Herndon, Northumberland, Pa Father: Peter STEPPE; Mother: Henrietta GROW Phoebe's Other Spouse: BICKHART Source: patron submission

2.  1880 Census Every-Name-Index/Images (online at Ancestry.com, Image #5 of 19):  Point Twp., Northumberland Co., PA, Roll T9_1164 (Book 1), p. 355A, PN 5, SD 3, ED 159, enumerated 4 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	9	10	13	24	25	26
41	41	Straub John A	W	M	22			/	Miller	PA	PA	PA
		______ Phoebe	W	F	21	Wife		/	Keep House	PA	PA	PA
		______ Cora A	W	F	1	Dau	/			PA	PA	PA

3.  1890 Census:  the 1890 Census Population Schedules were destroyed.

4.  1900 Census Every-Name-Index/Images (online at Ancestry.com, Image #31 of 34):  Sunbury Borough, Northumberland Co., PA, Roll T623_1450 (Book 1), p. 224A, SN 16, SD 10, ED 163, enumerated 11 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

19

20

21

22

23

24

25

27

335

337

Straub John

Head

W

M

Jan 1856

44

M

23

PA

PA

PA

Auctioneer

0

Y

Y

Y

R

H

______ Phoebe

Wife

W

F

Jul 1856

44

M

23

8

6

PA

PA

PA

Y

Y

Y

______ Cora A

Dau

W

F

Jun 1880

20

S

PA

PA

PA

Warper (Silk Mill)

0

0

Y

Y

Y

Jones Bertha

Dau

W

F

Oct 1881

18

M

2

1

1

PA

PA

PA

Weaver (Silk Mill)

0

0

Y

Y

Y

Straub Minnie

Dau

W

F

Jan 1885

15

S

PA

PA

PA

Winder (Silk Mill)

0

0

Y

Y

Y

______ Ralph

Son

W

M

Sep 1885

14

S

PA

PA

PA

Weaver (Silk Mill)

0

0

Y

Y

Y

______ Eva B

Dau

W

F

Mch 1889

11

S

PA

PA

PA

At School

9

Y

Y

Y

______ Nora M

Dau

W

F

Jul 1893

6

S

PA

PA

PA

9

Jones Florence

GDau

W

F

Oct 1898

1

S

PA

PA

PA

5.  1910 Census Index/Images (online at Ancestry.com, Image #8 of 34):  115 Tenth Street, Sunbury Borough (Ward 9), Northumberland Co., PA, Roll T624_1384 (Part 2), p. 236B, SN 4B, SD 12, ED 119, enumerated 16 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	19	20	23	24	25	26	28
*	115	91	93	Straub John A	Head	M	W	53	M1	31			PA	PA	PA	Eng	Auctioneer	General sales	OA	Y	Y		R	H
				______ Phoebe A	Wife	F	W	52	M1	31	9	7	PA	PA	PA	Eng	None			Y	Y
				______ Nora M	Dau	F	W	16	S				PA	PA	PA	Eng	Enterer	Silk Mill	W	Y	Y	N
*Tenth Street

6.  1920 Census Index/Images (online at Ancestry.com):  John is deceased.  The index is not every-name, so I can't directly call up Phoebe, but I don't find any BURKHART (or any variation I can think of) in Northumberland Co., PA.

7.  1930 Census Index/Images (online at Ancestry.com):  still unable to pull up Phoebe under any search terms I can think of.

8.  Family Group Sheet No. 55256 (Everton Publishers, Inc., P.O. Box 368, Logan, UT 84323-0368; Broderbund CD-14).

9.  LDS.  Family Search: Internet Genealogy Service: Ancestral File.