Thanks very much for the reply. Benjamin Purdum apparently didn't leave a will. I have copies of the adminstration as well as the court record entry for the suit brought by the heirs of Benjamin Purdum--they were splitting the land he left. The complication was that he apparently had divorced his wife Catherine and married an Elizabeth Brown just a few years before his death. Elizabeth had one child before marrying Benjamin, but the inventory refers to "her children." There are two entries in the court record, both of which name John and James Abernatha/Abernath, but neither Sarah nor Isaac are mentioned nor any children by Elizabeth, if they were Benjamin's.
In 1830, Samuel Abernathy, age 20-30, was living immediately next door to Benjamin Purdum in Ross County, Ohio. You probably have that information. From what you've written, the male child under 5 must be John, son of Samuel and Casandra, and the 15-20 year old is possibly William Abernathy, the one who is living next door to the older Samuel in Brown county in 1840, and the one living next door to Samuel and Mary Abernathy in 1850.
The woman on the 1840 Ohio Clermont, Jackson census was 20-30, so that could be either Casandra or Mary. I will look for a marriage record for Mary A.
I am so pleased to be able to identify John and James Abernathy. I had not identified Benjamin and Catherine Purdum's oldest daughter Casandra, either, until I came upon some of your notes.
I haven't located John Abernathy in 1860, but I did find a possibilty for James. There's a 28 year old James J. Abernathy, born Ohio, in Leavenworth, Kansas Territory, with a wife Elizabeth and infant daughter, unnamed.