Hi Jac
There looks to be at least three possible siblings to Ebenezer. IGI show three entries to the same parents, William and Mary, all in Kelso:
John SIMSON Birth: 06 Dec. 1786 - a submitted entry but I think it shows on SP
Anna SIMSON Christening on 5 April 1789
Helen SIMSON Christening on 27 Feb. 1791
Not all Parish Register entries have survived over time unfortunately. Banns/marriage for parents show in Kelso on 16 Dec. 1785
Monica
