Hi Sharon. I may (or may not) have some good news/bad news. The bad news may be that I think that I have some other candidate Dunbar daughters' spouses than the ones that you mention from Orange County, IN. From the searchable database at the Indiana State Library web site I have the following:
Elizabeth Jane Dunbarr m. Jeremiah Taylor 5 Jan 1834 Martha Dunbarr m. George Duckworth 6 Apr 1831 Robert Dunbar m. Sarah Mathews 21 Feb 1837 Mary Dunbar m. John J. Richards 15 May 1845 Margaret Dunbar m. Alsey Ferrill1849 Letitia Dunbar m. Williams Vandars 12 Sep 1840
All marriages occuring in Posey County. The last one is actually William Sanders, not Vandars. These all seem reasonable as seen from census determined ages, and I have tracked several of them down through additional federal censuses in Lynn and Black Twps. in Posey County. I'm making an effort to confirm via other records, and will advise.
The good news is that this may set the record straight. Hopefully, We'll see.