I am not a descendant, but several of my Amerine ancestors married into the Tatman family during the mid 1800's in the Hocking Co., OH area. In the quest of trying to find the parents of these spouses, I became very intrigued by this large family. I've been working on trying to put together family groups of these Tatmans going back to at least one of the four ancestors from Allegany Co., MD: Joseph, James, Benjamin, or Thomas.
Please let me know if you are able to connect your Sarah E. Tatman as the daughter of Amos. If so, I can give you more info concerning his parents and siblings. Do you have the death date of Sarah (Tatman) Seitz? She died between the 1870 and 1880 census. Do you have the names of her children?