Are you working backward from the William Crumpler that you are sure of? If so, the obvious questions are:
What men named Crumpler were in the area in 1670?
What were William's children's names, and did the people there have a naming pattern?
Did anyone leave him anything in a will?
Was he involved in any land transactions? Did he give up rights to land to someone else?
Did he live next to someone older named Crumpler?
etc.
While gathering the links below, (Googled "Isle of Wight genealogy") I noticed marriage and death records but a lack of mention of birth records. Didn't they keep any in Isle of Wight County?
http://vagenweb.org/isleofwight/http://www.usgwarchives.net/va/isleofwight.htmhttp://genealogytrails.com/vir/isleofwight/http://www.iwchs.com/ [Isle of Wight County Historical Society]
https://www.genuinesmithfieldva.com/genealogical-research.htmlhttps://www.raogk.org/virginia/isle-wight-county/ [looks like Random Acts of Genealogical Kindness local chapter]
https://www.familysearch.org/wiki/en/Isle_of_Wight_County,_Virginia_Genealogyhttp://www.linkpendium.com/isle_of_wight-va-genealogy/And here is something I found on ancestry.com, from a book of abstracts of wills from IOG County. There were other Crumplers mentioned, but this seemed the best one for now. The book itself is probably available at a real good genealogy society library or one local to Isle of Wight. I think the page number was the transcribers reference to the original will book.
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Phillip Rayford: Leg. son Robert; daughter Mary; daughter Anne; daughter Patience; to son Robert all the cattle at John Person's; daughter Sarah; son William; son Mathew; son Phillip; wife. Son Robert, Ex. Brother-in-law William Kinchen and brother-in-law William Crumpler, trustees. D. July 23, 1724. R. December 28, 1724.
Wit: John Crumpler, William Crumpler, Jr.
Page 164
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From
Wills and Administrations of Isle of Wight County, Virginia, 1647-1800, Book II
By Blanche Adams Chapman, reprinted ... with a consolidated index by Jessica Budick and Anita Comtois,
Originally published Smithfield VA, 1938
reprinted, etc. Baltimore: Genealogical Publishing Co., Inc, Baltimore, 1975
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Other than that, I am lost or over my head. I waded through some early NE records for my wife's family, but haven't worked with anything in VA at all.