The marriage you listed, William GREER m. 27 May 1814, Matilda HYDE, Prince George's Co., MD, is on RootsWeb, which also has
Moses GREER, b. 1716, Gunpowder, Baltimore Co., MD, m. Mary BAILEY / BAYLEY. They had Aquila GREER (9 Sep. 1760, Baltimore Co. - 1842, Fairfield Co., OH), who m1. ca. 1780, Mary _; & m2. ca. 1833, Lucinda FULLER.
Bill & Martha REAMY's St. James Parish Register, Baltimore Co., 1787 - 1815: Aquila & Mary GREER had James, 6 Feb. 1790, & Wm., 31 Dec. 1791.
Aquilla GREER & Mary had (per RootsWeb)
Harriet, b. 5 Mar. 1788
James, b. 6 Feb. 1790
William, b. 31 Dec. 1791, m. 27 May 1814, MD, Matilda HYDE.
Mahala, b. ca. 1795, m. Jacob STEWART
Mary, b. ca. 1800, m. 10 Feb. 1820, Harrison Co., OH, Aaron PUGH.
On Censuses of 1820 - 1840, Wm. GREER was of Amanda Twp., Fairfield Co., OH. Wm. & Matilda had a large family including sons John (10 Nov. 1821 - 28 Nov. 1869) who m. 12 Dec. 1852, Pickaway Co., OH, Mary America WRAY. John is buried in Van Horn Cem., Hancock Co., OH, off County Road 169 about three miles west of Value, OH. Wm. & Matilda also had son William. He could be the one of Liberty, Fairfield Co., OH, 1880: GREER, William, 62, OH MD MD; wf. Amelia, 52, OH VA VA; dau. Mary, 28, OH.
FamilySearch database of the 1880 Census, Delaware, Hancock, OH:
GREER, John, 68, MD MD MD; wf. Mary, 67, OH PA PA, son Jefferson, 24, OH.
Amanda, Hancock, OH: GREER, Ford, 28, OH MD OH; wf. Catharine, 25, OH PA OH; ch. b. OH: Wm. D., 8; Jefferson M., 5; Earl E., 3; Virgie A. (female), 11 mos.
Madison, Hancock, OH: GREER, Jeremiah, 48, OH MD PA; wf. Amanda, 46, OH; sons b. OH, Holland M., 26; & John C., 17.
Marion, Hancock, OH: GREER, wid. Mary K., 54, OH PA PA; son Wm. H., 26; Robert P., 24; Franklin J., 20; & Milton, 13, all b. Ohio.
Mt. Blanchard, Hancock, OH, GREER, Henry, 62, OH MD MD; wf. Eliza, 63, OH.
There were other younger GREER families of Hancock Co., OH, 1880.
USGenWeb has a bio of Samuel Ford GREER (1851, OH - __ ) son of John GREER (15 May 1812 - 24 Oct. 1882) & Mary BROWN (Je. 1813, Pickaway Co., OH - living in 1886).
John GREER & Mary, of Delaware, Hancock Co., OH, in 1880, had
Joshua, d. California [CA]
John, to CA
Sarah ARMSTRONG, to MO
Henry, to CA
Eliza, to CA
Nathan, to CA
Mrs. Ellen COLE
Charlotte, m. 2 Jan. 1874, Isaac F. ELDER, & had Muzetta, Zoa, Zeller, Squire, Zana, & Frank.
Samuel F., m. 16 Feb. 1871, Catherine CORBIN
Mrs. Harriet MESSIMORE
Jefferson, 24 in 1880, to CA
Samuel F. GREER & Catherine had [Wm.] Darwin, Jefferson, [Earl] Elmer, Virgie, Bertie, & John.
William J. GREER & wf. Sarah, natives of Maryland moved to the Blanchard settlement in 1825. They were Methodists. They had
Wm. J., m. ca. 1827, Rosannah ELDER, dau/o Robert
Charlotte, m. 14 Sep. 1826, Asa M. LAKE
Maria, b. 1827.
Robt. BARNES' Baltimore Co. Families, 1659 - 1759:
James GREER was transported to Maryland ca. 1674 and settled in Baltimore Co., where he m. Anne, dau/o Arthur TAYLOR, who on 6 Je. 1687, conveyed 75 acres of "Arthur's Choice" to Ann & James GREER. Ann m2. Laurence RICHARDSON, who held the above land in trust for the orphan sons of James GREER. Ann m3. Oliver HARRIOTT. James GREER & Ann had John, b. ca. 1688; James; & perhaps Joseph.
John (ca. 1688, living in 1747) m. Sarah DAY. Will of Sarah, widow of Nicholas DAY, in Oct. 1730, named her dau. Sarah, wf/o John GREER. John & Sarah had Wm.; Moses, b. 1716; John, b. 1718; Aquila, 1719; twins Sarah & Ann, b. 15 Feb. 1721; Benjamin, b. 6 Jan. 1727/8; & Joseph, b. ca. 1729.
Moses GREER, b. ca. 1716, m. Jan. 1737, [records of St. John's & St. Geo.], Baltimore Co., Mary BAYLEY, and moved to Pittsylvania Co., VA. They had Lawrence, b. 7 Je. 1757, & Aquila, b. 9 Sep. 1760.
Pr. Geo. Co., MD, Indexes of Church Registers,
St. Paul's at Baden: Mary Ann GREAR, bu. 11 Aug. 1867, aged ca. 76.
Henry GREER & Mary had Cornelius L., b. 30 Apr. 1833.
Fielder W. GREER m. 3 Oct. 1865, Margaret V. WATSON.
King Geo. Parish: Fielder W. GREER d. 5 Apr. 1875, aged ca. 40.
Gust SKORDAS' Early Settlers of MD (from land records) James GREAR was transported by 1674, Lib. 18, Folio 152.
I've shown the sources of the above information, but remember that all data needs to be verified. THAT should keep you busy!