Actually, since I posted this message I have had many breakthroughs on my ALEXANDER line and their origins. Thank you for reminding me to post my findings!!
The lack of an 1890 Census made it difficult, but fortunately, Norfolk had very thorough and consistent city directories at the time, which helped to fill in many blanks and verify connections between the information I already had and the possible matches I was finding in VA & NC...
Turns out, my grandfather was James M. ALEXANDER (m. Mary Ann FITCH who remarried after his death, to a man named MEARS). James and his brothers Walter and Henry were all boatmen, captains of assorted sailing vessels (Tugboats, Steam Ships and the like), and all three had migrated to Norfolk, VA by 1890, where they all appear for many years in the Norfolk City Directories, which were complete with not only addresses, but also occupations and reverse lookup sections to see who else they were living with. (Seriously, if you are trying to research anybody in the Norfolk, VA area, make use of these directories, as they are a *wonderful* resource! They are all online here: http://www.npl.lib.va.us/smrt/smr_home.htmlhttp://www.npl.lib.va.us/smrt/smr_home.html )
As suspected, my g-grandfather was not originally from Norfolk. Turns out, he was from Tyrrell County, NC. His parents were James Monroe ALEXANDER and Caroline E. L. DILLON. In addition to the aforementioned Capts. Walter and Henry, his other siblings were: William D., James R., Sarah Ann, Florence, Alvaro, Robert and Harriett. Of all of the boys of this generation, only the three who migrated to Norfolk were still alive in 1890.
Beyond that generation, James Monroe's father's name was William ALEXANDER. I do not have any information yet about his mother. Caroline's parents were Alexander DILLON and Sarah WYNNE.
Alexander DILLON's father was James DILLON. Sarah WYNNE's parents were Robert WYNNE and Zillah TARKINGTON. One of Caroline's brothers, Henry E. was featured in the book "Cyclopedia of Eminent and Representative Men of the Carolinas of the Nineteenth Century", which is readily available in its entirety through Google Books.
I haven't gotten any further back than that yet (researching other family lines as well), but there are several readily available family trees for the DILLON line. Of course, how many among them are sourced remains to be seen... ;-)
I do not see any immediate connections to your line as described here, but who knows what I will find when I try to move beyond William ALEXANDER (b. ca 1795 in Tyrrell County, NC), to see where he came from...