Here are the 2 Sybil's, different parents. Joshua's wife b. 1774, daughter of Nicholas. Ephraims wife, b. 1747, likely daughter of James. I would just disconnect the one born in 1747, from Joshua.
In your question, you indicate that Joshua married 2 Sybil's. I believe that is incorrect, after Sybil died in 1799, he married Betsey Patterson, likely Sybil's sister noted below.
Sybil Patterson (daughter of Nicholas) https://www.wikitree.com/wiki/Patterson-16406
born at Harvard, Massachusetts - should likely be left as Joshua Davis' wife.
: Patterson, Sybel, d. Nicholas and Anna. Jan. 31, 1774.
: Patterson, Betsey also born at Groton: Betsey, d. Nicholas and Anna, July 31, 1776. From: Baldwin, Thomas, compiler, Vital Records of Harvard, Massachusetts to the Year 1850, NEHGS, Boston, Massachusetts, 1917
: Davis, Joshua, and Sybil Patterson of Harvard, at Harvard, Aug. 3, 1793.
: Davis, Joshua, and Betsey Patterson, May 31, 1801
: Davis, Sibel, w. Joshua, Jan. 8, 1799. [a. 25 y. GR2] From: Vital Records of Groton, Massachusetts to the End of the Year 1849, Volume II: Marriages and Deaths, The Essex Institute, Salem, Massachusetts, 1927
Sybil Patterson, wife of Ephraim Brown, likely daughter of James and Mary https://www.wikitree.com/wiki/Patterson-17374
: Patterson, Sibbel, d. James and Mary, July 22, 1747. From: Vital Records of Groton, Massachusetts to the End of the Year 1849, Volume I: Births, The Essex Institute, Salem, Massachusetts, 1926
Patterson, Sybel, and Ephrm Brown, Mar. 31, 1768. From: Tolman, George compiler. Concord, Massachusetts Births, Marriages, and Deaths, 1635-1850, Printed by the Town, T. Todd Printer, Beacon Press, Boston, Massachusetts, 1891