Here is some data for John Mercer, the brother of Jemima Gately Mercersome of which indicates that he had a connection to DR. John H. Bush who md. Mary Rowland and William Bush who md. Mary Thetford.
John Mercer born 6/4/1764 SC (cannot confirm) and died 4/8/1827 Caldwell Co., KY.THis death date seems to be correct and is supported by Caldwell Co. court records.
Caldwell Co. Inventory, Estate and Settlement Book I:294 5/17/1827: Appraisal of Estate of John Mercer, dec'd ordered. Administrators as William and John Mercer. rec. 10/15/1827 I:320 8/8/1828: Settlement of estate of John Mercer, dec'd. Administrators as William and John Mercer. Appointed to conduct appraisal - Thomas Haynes and Reuben Rowland.
The above Reuben Rowland was the brother in law of Dr. John H. Bush.
Livingston Co., KY Court Book 1806 Micajah Rowland (s/o dec'd) and John Cook (sil dec'd) came into court and entered into bond with James Mercer and James McNabb as security as Executors for the Will of Reuben Rowland.
The above Reuben Rowland was the father in law of Dr. John H. Bush.
Caldwell Co., KY Deed Book 11/22/1809 William Bush grants Power of attorney to John Mercer to convey 100 acres in KY to George Bush originally granted to William Thetford. Witnessed by George Bush and William Banister.
William Bush married Mary Thetford, d/o Simon Thetford ca 1795 in Laurens Co., SC. Both families then located to Caldwell/Livingston County in KY ca 1800. Simon Thetford's other daughter Rebecca married James Banister also of Caldwell Co.Simon' Thetford's father walter Thetford left a will in 1767 in Orange Co., NC. (Orange, Person and Caswell County formed from Caswell)
Not conclusive enough to prove that Mercer and Bush were related but certainly they appear to have been close friends.Makes you wonder just where Mercer Bush got his name, doesn't it??