Hi I can trace my Drinkwater line to Richard James Drinkwater who is the older brother to your John Sydenham Drinkwater.
I can tell you he (John) was not born in Wales at all.He was christened on the 13th July 1821 in Ledbury, Hereford, England. His parents being Thomas Jamesand Ann. His father died in 1823 and his mother re-married a George Boulter and moved the family to Wales after 1835.
I am after information on his mother Ann (Mary-ann I believe) I can not find her maiden name at all. I know she was born in 1795 in Sydenham, Kent, England and I believe she married Thomas James in 1811 but can not be sure.
I have a bit more info if you are interested. Cheers Jacqui