Re: Isaac R. Doulin 1848 - 1923 Lancaster County, Pennsylvania
The 1850 census shows an Isaac Dulin 2 living with John 25, Rebecka 21 and Mary 4/12 living in Drumore Twp., Lancaster County. It shows John as born in Maryland.
Based in the 1860 census I'm guessing Mary and Isaac were orphaned. There might be an Orphans Court record of guardianship for them at the Lancaster County Courthouse.