I am in agreement that Mary's husband was Andrew: 1) Record of Andrew Gibson's estate, Mary administrator, with Thomas Douglass as one of the men who inventoried the estate.Andrew had enough resources that he was able to loan money to 3 men.9 children mentioned but not named.Mary Gibson Cooper named 10 children in her will indicating a child not yet born in the estate settlement of Andrew, or an older child above the age of maturity who would not be part of the estate settlement of his father.
2) Thomas Douglass is named as guardian of Mary's6 children *after* her marriage to John Cooper.Undoubtedly she did not want her husband to have any say over the rearing of her children and hence John Cooper was not named guardian.Why would she marry a man she did not trust?
3) Mary was wealthy enough that she did not want John Cooper to have control, and Thomas Douglass was witness to that prenuptial agreementSee Item #1
The common thread is Thomas Douglass.Are we sure her maiden name was Duncan?Could Thomas Douglass have been a brother or other close relative to be guardian to her children rather than a Gibson brother to her husband?In most cases a guardian was a close relative.
Notice that Mary's Gibson's will names her as Mary Gibson, not Mary Cooper, her second husband's surname.She must have been a very strong-willed woman or John Cooper was deceased and she took back the name of her first husband, and/or the second marriage was merely one of convenience for financial reasons/estate management.