Hallo,
sorry, but I do not know much more about this KÖSTER-family from parish Obernkirchen (in hessian earldom of Schaumburg).
If you want to find out something about your KÖSTER-ancestors, it will be helpfull to tell the parish and the century you search for them!
Greetings from Germany,
Felix Arndt
felix_arndt@gmx.net