I can't help you too much on Mary DeMarcus. My connection is the Mary Walter DeMarcus that married Jacob Pethel. I do not have a Sarah Estelle, but do have a Sallie E. DeMarcus, granddaughter of W.A. Demarcus and Caroline R. DeMarcus.Sallie was born around 1867.Sarah is not the daughter of Jacob and Mary. They had only five children and they were born in the time period of your Sarah E.I am very interested in any thing you find out on the DeMarcus family since we are tied to them also.Stay in touch.