I have a possible connection for you, though it's not much and I'm looking for more information myself.
I have an Anna Maria Allen.She was born abt 1801 possibly in MD.She married on 1/16/1824 in Alexandria, VA to Ezekiel S. Jones (1790 Alexandria, VA to 7/3/1879 Alexandria, VA). Ann Maria Allen Jones then died 12/11/1883 in Alexandria. Ezekiel and Ann Maria had 6 children that I know of:
1) Anna Lucretia Jones (12/10/1824 Alexandria - 10/6/1900 Alexandria) married on 3/17/1842 to William Stephen Moore of Alexandria, VA. 2) James W. Jones (b. abt 1828) 3) Ezekiel S. Jones, Jr. (b. abt 1833) 4) Henry C. Jones (b. 1836, Alexandria; d. 4/1/1874 Alexandria) m. Amanda ???. 5) Jane E. Jones (b. abt 1839) 6) George W. Jones (b. 6/20/1839 Alexandria; d. 4/2/1896 Wilkes, Alexandria, VA) m. bef. 1893 to Elmira ??? who died on 4/18/1900.
It could be that this Ann Maria Allen could be a sister to your Julia Ann and your Mary of Alexandria.
I also know a little about the Moore family that Anna Lucretia Jones married into.
William Stephen Moore (11/21/1821 Alexandria - 3/24/1894 Alexandria) was the son of Joseph C. Moore (abt 1798 Alexandria - 6/8/1867 Alexandria) and his wife Mary A. Morgan (1/29/1802 Richmond - 12/9/1877 Alexandria).They married on 9/15/1819, probably in Richmond. Joseph and Mary Moore had 6 children that I know of:
A) William Stephen Moore - previously mentioned. B) Joseph Wedderburn Moore (abt 1825 Alexandria - 6/13/1860 Farifax St, Alexandria) married Mary Jane Allen (1825 - 12/21/1914 Alexandria) C) Thomas Munroe Moore (4/15/1828 - 10/1828 Alexandria) D) David Moore E) Cornelius A. Moore (Abt 1834 - 3/11/1875 Alexandria) married Eliza Hill (Abt 1835 - 5/19/1890 Alexandria) F) Norman F. Moore (Abt 1838 - 8/7/1888 Alexandria) married Annie ???
It would not be unreasonable to suppose that brothers William S. and Joseph W. Moore married sisters Ann Maria and Mary Jane Allen.