Re: Isaac R. Doulin 1848 - 1923 Lancaster County, Pennsylvania
I suggest would getting their death certificates and obituaries. You might also see if there is a church or pastoral record of their burials.
Check with the Lancaster County Historical Society and the Southern Lancaster Historical Society to see if they can help you with the church records and obits. Hopefully, if nothing else the obits list siblings. The death certificate you have to get from the PA Div. of Vital Records.
There was an Isaac R. Doulin who served in the 83rd PA Inf during the Civil War.