— born in Washington Twp., Putnam Co., IN:
4.  James D. "Jay" HATHAWAY, b. 1853/4
5.  Anna A. HATHAWAY, b. 1855/6; d.s.p. by 1870
6.  Mary HATHAWAY, b. 1857
7.  Douglas HATHAWAY, b. 1860/1
8.  Martin HATHAWAY, b. 1863/4
9.  Lee G. HATHAWAY, b. 1867/8

1.  Anon.  1966.  Marriage Index:  Ohio, 1789-1850.  Liahona Research, Orem, UT (Broderbund CD-400):  not found.

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

Sylvester HATHAWAY Birth: Abt. 1816, Warren, Ohio Father: John HATHAWAY; Mother: Elizabeth Source: none given

Milton Fillmore HATHAWAY Birth: 31 May 1830, Warren, Ohio Father: John HATHAWAY; Mother: Elizabeth Source: none given

3.  1850 Census Index/Images (online at Ancestry.com; Image #17 of 51):  Town of Lebanon, Turtlecreek Twp., Dist. 149, Warren Co., OH, p. 29A/57, 409/410, enumerated 7 Aug 1850, official enumeration date 1 Jun 1850 (extracted by Diana Gale Matthiesen):¤•

Sylvester Hathaway	32	M		Cabinetmaker	300	Ohio
Harriet      "	22	F				O
Ephraim M    "	2	M				O
W.V.         "	10/12	M				O

Living next door to Sylvester's parents, John & Elizabeth HATHAWAY (both æ 57, b. PA).

4.  1860 Census Images (online at Ancestry.com; Image #282 of 530):  Reelsville P.O., Washington Twp., Putnam Co., IN, p. 282, PN 142, 987/978, enumerated 20 Jul 1860, official enumeration date 1 Jun 1860 (extracted by Diana Gale Matthiesen):¤•

Sylvester Hathaway	44	M	W	Farmer	620	300	Ohio
Harriet      "	38	F	W				"
Ephraim M    "	11	M	W				"
Martha A     "	9	F	W				"
Jas D.       "	6	M	W				Indiana
Anna A       "	4	F	W				"
Mary         "	2	F	W				"
Milton       "	28	M	W	Farmer	620	300	Ohio
Elisabeth    "	65	F	W				Pennsylvania
Hulda Davis	49	F	W				"

Elizabeth is Sylvester's mother; Milton is Sylvester's brother.  I don't know how Hulda fits in.  And, yes, the property values were the same for both Sylvester and Milton, suggesting they've just inherited from their father's estate.

5.  1870 Census Images (online at Ancestry.com; Image #15 of 48):  Cloverdale P.O., Washington Twp., Putnam Co., IN, p. 266A, PN 107, 765/765, enumerated 28 Jul 1870, official enumeration date 1 Jun 1870 (extracted by Diana Gale Matthiesen):¤•

Hathaway S	45	M	W	Farmer	3200	1168	Ohio
"    Harriet	42	F	W	Keeping house			"
"    Ephraim	21	M	W	Farm Laborer			"
"    Alice	17	F	W				"
"    Jay	16	M	W				Ind
"    Mary	13	F	W				"
"    Douglass	9	M	W				"
"    Martin	6	M	W				"
"    Lee G	2	M	W				"

6.  1880 United States Census and National Index (LDS Family History Resource File: CD-ROM Library):  neither Sylvester nor Harriet HATHAWAY found, anywhere.