Mercy Kingsbury was the wife of Richard Briggs, Jr. born 1/12/1678/69. His father was born in 1638/39. They were married about 1707 and had four children. This is documented in the Family History Library and also in "A Briggs Memorial" by Rev. Everett Francis Briggs and in "We and Our Kinsfolk" by Mary Balch Briggs.I'm descended thru his son James born 1718.
According to the Family History Library there was another Mercy Kingsbury Born in Dedham, MA on 11/10/1677 and who married Samuel Parker.There are also some other records in the Family History Library that mix up the two.
I'm confident that Mercy was married to Richard Briggs as this line (called John Briggs of Taunton) is well documented.