You'll find Harvey and Harriett in the 1930 census. I believe they are also in the 1900 census under the spelling of Kennett. You'll also find them in the 1910 census under the spelling of Grahbe and Gnehm. It's not spelled that way in the census just in the index. I couldn't find him in the 1870 census.
You can look at some of these records for free at labs.familysearch.org and Ancestry.com. For those you cannot see for free check with your local libraries to see if they have Ancestry or Heritage Quest.
If you haven't already I suggest trying to get Harvey's death certificate and obituary. Hopefully the latter will if nothing else give any siblings he may have had.
See if the Lycoming County Genealogical Society can help you with the obit. The Columbia County H & G Society may be able to help you find a baptismal record for him.