Sorry, I didn't identify parents of Justinian JEFFERSON, but, considering that some of the surname arrived in Maryland by 1668, there were not very many in the state. You may need to find the church where Justinian was baptized or he and his parents married because there do not seem to be marriage licenses for them.

Do you have the Revolutionary War Pension, S30508, for Justinian JEFFERSON? On 7 Je. 1842, Mason Co., KY, he said he was of Montgomery Co., MD, until about 1794, when he moved to Mason Co., KY, where he was 83 on 2 Sep. 1841. [Montgomery Co., MD, was formed in 1776 from Frederick County, which was formed in 1748 from Prince George's Co. Also, consider that Justinian may not have known exactly how old he was in 1841. He may have been born later.]

These are the earliest records I see for JEFFERSON of Maryland.
Gust SKORDAS' Early Settlers of MD (from land records, transported by others) JEFFERSON:
John, of Dorchester Co., by 1668, service 1677, Lib. 11:581 & 15:431
James & Ralph, both by 1671, Lib 16:411.

MD Calendar of Wills: John JEFFERSON, Dorchester Co., 30 May 1767, pr. 28 Nov. 1769. To wf. Rachel, exx., & unborn child. To bros. Thomas, Henry, & James. Wit. Jonathan PATRIDGE, Leven WALLER.

BRUMBAUGH's MD Records...Bay Hundred, Talbott Co., 1776, JEFFERSON, Francis, Geo., & Thom. (heads of household). /
St. John & Pr. Geo. Parishes, 1776, JEFFERSON, Luke, 44, 8 [ages of Luke & a male in household]; Elizabeth, 43. /
Oaths of Fidelity, Pr. Geo. Co., 1778, Luke JEFFERSON.

Abstracts of Wills of Montgomery Co., MD, 1776 - 1825--only one will for JEFFERSON:
Benjamin of Calvert Co., will pr. 16 Aug. 1788, Montg. Co., ch. Henry & Hambleton (coexs.), Basil, Leonard, John, Violetta, & minor son Wm., c/o his uncle Edward WOOD. Wit. Isaiah BOONE & Robert BRIGGS.

Prince Geo. Co., Indexes of Church Registers, King George Parish, JEFFERSON, Thomas & Holley had Hepsabah, b. 6 Sep. 1793
Joshua & Lottie had Sarah, b. 18/19 Apr. 1792 (entered on pp. 380 & 400).

Robert BARNES' MD Marriages, Fredk. Co., JEFFERSON:
Henry, 16 Dec. 1780, Mary HOWARD
John, 5 Jan. 1779, Masey? GRAY.

Margaret MYERS' Marriage Licenses of Fredk. Co., MD, JEFFERSON:
Benjamin, 6 Jan. 1783, Prescilla JEFFERSON
Deborah, 2 Mar.1803, John MICHAEL
Elizabeth, 5 Apr. 1802, Christian HILL
Hamilton, 7 Dec. 1826, Ann Sophia KOONTZ
Henry, 16 Dec. 1780, Mary HOWARD
Rebecca, 22 Dec. 1801, Edward FITZGERALD
Henry, 2 Mar 1807, Elizabeth FITZGERALD
Leonard, 3 Dec. 1806, Barbara NICHOLS.

Marriage Lic/o Montgomery Co., MD, 1798 - 1898, JEFFERSON
Hester A., 4 Je. 1856, Thos. F. CASHELL
Lydia, 4 Je. 1856, Geo. KENDALL
Rhoda, 28 Nov. 1803, John HENRY.

Mason Co. KY, Marriages:
Samuel JEFFERSON, 10 May 1810, Margaret(te) SANDERS, bondsman & witness John STEPHENSON/ STEVENSON, with permission of her parents Clement & Susana WALTER.
Elizabeth JEFFERSON m. 21 Sep. 1814, Asa WATSON, bondsman Justinian JEFFERSON.
Perry JEFFERSON, 24 Mar. 1817, Nancy SMALL, bondsman Thos. MORGAN.

Online message: Elcana JEFFERSON (9 Sep. 1797 - 11 Je. 1877) m1. 7 Jan. 1822, Rachel SAUNDERS (1 Sep. 1799 - 24 July 1836); m2. 19 Mar. 183_, Eliza HOLLIDAY (15 Feb. 1805 - 1 Sep. 1862) all three bu. Shannon Cem. See FindaGrave.

Jesse JEFFERSON is listed online in these records:
Married 15 Je. 1827, Mary JACKSON, permission of Elizabeth JACKSON, wit. Judy JACKSON, bondsman Wm. GRIFFITH.
Dist. 3, Mason Co., KY, Jesse JEFFERSON, 1850, aged 45.
Census of 1860 Mortality Schedule, Jesse JEFFERSON d. Aug. (1860?), aged 53.
Bondsman for marriages of Rebecca JEFFERSON, 8 Mar. 1848, Enis W. POE; also Mary J. JEFFERSON, 3 Sep. 1859, David CALDWELL.

Jacob JACKSON was bondsman for marriage of Rebecca JEFFERSON, 17 Nov. 1830, George WATSON.
Jacob Y. T. JACKSON was bondsman for marriage of Keziah JEFFERSON, 2 Je. 1847, Wm. A. CAMPBELL.

Samuel JEFFERSON was bondsman for marriage of Lorand JEFFERSON, 7 Aug. 1827, Jacob JACKSON; also Susan JEFFERSON, 1 Oct. 1835, Joseph WILSON.

One Perry JEFFERSON was sheriff of Mason Co., KY, in 1884.

Google Pilot.FamilySearch.org. That has copies of the 1850 census. Elcana is indexed Eleana, but the actual census shows
Elcana JEFFERSON, 52, Eliza, 42;
Sarah Ann, 25; Louis, 23; Amos, 21; Eliza, 16; Elizabeth, 14; Louis R., 6.
[If death date above for Rachel is correct, only the last child would have been by the second marriage.]

1850: Jesse JEFFERSON, 45; Mary, 35; Cane, 16; Elizabeth, 12; Albert, 3; Katharine, 1.
[There were also Jesses aged 35 & 29 in 1850.]

1850: JEFFERSON, Henry, 32; Abigail, 28; Perry, 8; John, 6; Nancy, 2
Also in household, Ezekiel POE, 28, & John McLEAN, 25.

1850: JEFFERSON, Nancy, 45 [wid/o Perry?]; Thomas, 13
Also in household, HUNT, John, 30, & Mary, 22; MILLER, Susan, 40.

It's helpful to have the children in a family in chronological order. That shows that the elder children could not have been Polly's if she was born in 1785. She most likely had son Jesse in 1805, but it's unlikely she had Justinian in 1838 when she was 53 & husband Justinian was 80. Justinian, b. 1838, must have been a grandson.

Perry (8 Mar. 1789 - 1 Mar. 1845, FindaGrave) m. 1817, Nancy SMALL?
Mary, b. 1789?
Elizabeth, b. 1793, m. 1814, Asa WATSON?
Elcana (1797 - 1877)
Sarah (1798 - 1879)
Jesse (1805 - 1860) m. 1827, Mary JACKSON?

Who was Nancy BLAND JEFFERSON? (5 Feb. 1801 - 15 Apr. 1887) bu. Shannon Cem., per FindaGrave.

--not my family