Judy:I am not related to your particular Casner line.However, while researching my Casner line, I keep track of any Casner line that I come across in an effort to keep from going down the same path over and over.I maintain your Casner line in my data base 0008.The following information I have gathered from census records and will give you locations of where to further look for your line.
The father of Stephen Harry Casner is Joseph Casner and his wife Alice.According to the 1870 NJ census, Joseph was 60 years of age and born in NJ.Alice was 62. Stephen is one of four children living with them (Elwood, Joseph, Mary G. and Stephen).I looked at the on-line 1860 census record for Joseph and In looking at the 1860 census and Theodore is in the home at that time, along with two other children whose names are not readable on that census.
On the 1860 census and the 1870 census Joseph Casner and his family are in Middlesex County, NJ, Monroe Township.On teh 1870 census, the post office is Prospect Plains.On the 1870 census, Theodore Casner is living next door to Josephy.On the 1860 census he is living in the home with Joseph, so therefore, Theodore Casner is a brother to Stephen Harry.There is a Morgan Casner on the 1870 census who is the same age as Theodore and may be a twin.On the 1860 census, the names of two children cannot be read.
I would suggest you go to a library that has census records on hand and search the 1850 thru 1900 census records in NJ.Also, you might want to check the volunteer sites (GEnie Angles, Helplist, RAOGK) to see if you can find someone there who can assist you.
I would also try to find if there is a genealogical/historical society in Middlesex County.Generally if you send a donation to the societies and be specific about what you are searching, you will have quite a bit of luck.You might also want to write to the Middlesex County Courthouse and see if you can obtain the record of the marriage of Stephen and Rosabelle.
According to the 1900 NJ census Stephen was born 10-1855 and Rosabelle was born 10-1850.
Hope this helps some. Keep in mind, all this information is from census records. Good luck in your continued research.