Mary Lawrence was born 6 Sep 1708 in Wrentham, Norfolk, Massachusetts. She was the daughter of Daniel and Mary (Wheelock) Lawrence. Note: There appears to be no instance of her being called Marcy or Mercy. Her birth record listed her given name as Mary. The Barbour Collection of CT Vital Records listed her given name as Mary when it listed the birth of her son, Peter Covell of Killingly, CT. Her father's will of 1747 listed her given name as Mary.
Note that the Barbour Collection of CT Vital Records does not mention any of her other alleged children.
Mary married Stephen Covell after 5 April 1729, when the birth of Stephen's child Stephen Jr, was recorded with his first wife Abigail. Some genealogies list Mary's marriage to Stephen as about 1721, before Stephen married Abigail. However, it is clear that Abigail was married to Stephen before Mary, since Abigail had Stephen Jr. in 1729 and Mary had Peter in 1742. Clear time precedence.
It has been incorrectly asserted that she was the wife of Thomas Fox (b. 1706), who moved from Boston, MA to Woodstock, CT. 
The error is made clear by examining the will of Mary's father, Daniel Lawrence: Will of 1747, Daniel Lawrence names children as follows; Daniel, Joseph, James, Samuel, Mary Covel, Esther Ballard, Marcy, John, Elihu and Asa.
Another book  states on page 63 that Thomas Fox (b. 1706) married a "Mercie (family name unknown)". It is left ambiguous as to whether he married in Boston, MA or Connecticut.
Another book dealing with Fox genealogy but published later than the one mentioned above, claims that the above mentioned Thomas Fox came to Woodstock, CT and married Mary (or Mercy) Lawrence of Killingly [CT].
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Mary is 19 degrees from Ferenc Liszt, 32 degrees from Frédéric Chopin, 29 degrees from Johannes Brahms, 32 degrees from Clara Schumann, 30 degrees from Fanny Hensel, 39 degrees from Jean Sibelius, 23 degrees from Edvard Grieg, 18 degrees from Richard Wagner, 27 degrees from Antonín Dvořák and 15 degrees from Kathie Forbes on our single family tree. Login to find your connection.