Gregory's use of a barometer to predict farming-related weather conditions led him to be accused of witchcraft by Presbyterian ministers from Aberdeen, although he was never convicted.
[3] His mother was Janet Anderson, whose father David was said to be exceptionally talented in the fields of medicine and mathematics.
When his elder brother Alexander died childless in 1664, Gregory inherited Kinnairdy Castle, just south of Aberchirder, Banffshire.
Twenty of his children reached adulthood and three, David (1659–1708), James (1666–1742) and Charles (1681–1754), were mathematics professors in the same period at British universities.
[9][10] Gregory moved to Kinnairdy Castle with his wife and children as soon as he inherited the estate and lands from his elder brother in 1664.
David corresponded with Edme Mariotte who shared an interest in atmospheric pressure and its measurement for meteorological prediction.
[4][11][12] Gregory passed the control of the castle and lands to his son David in 1690, who was by then the Savilian Professor of Astronomy at Oxford.
[13] Aided by an Aberdeen watchmaker, Gregory began designing a military cannon and showed the prototype to his son David.