Did your Humphrey die in 1756 or there abouts? If so he was probabley the son of Thomas Madison and wife Johannah of Caroline County, VA.
In 1903 Mrs. Elizabeth Laughlin Lord published at Portland, Oregon, Reminiscences of Eastern Oregon. She states the book is for the consumption of her family and in order that certain Bible records might be preserved, she inserts them in an appendix of her book which is in the Library of the National Society, Daughters of the American Revolution, Washington, D. C. Among the Bible records in this volume is that of Thomas Madison and Johannah, his wife.
Thomas Madison died January 20, 1754 and Johannah, his wife, died April 13, 1758. Their children were:
J. Madison born October 26, 1719
Ambrose Madison born March 11, 1724
Jane Madison born February 11, 1728; died October 24, 1767
Humphrey Madison born April 25, 1730; died September 12, 1756
Ann Madison born July 31, 1733
Sarah Madison born February 29, 1735; died October 31 1801. She married on November 27 1755, Thomas Laughlin who was born in England and came to America early 1700s; he died December 13, 1801.
Mary Madison born May 15, 1738
George Madison born October 7, 1740
Roger Madison born April 15, 1744; died September 12, 1768
Elizabeth Madison born Mary 30, 1747

 

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Also - note that most references and online family trees show Humphey Madison as a child of Thomas Madison's brother John Madison III and John's (perported) first wife Eliza Minor.  This is the only reference I've found that shows him as Thomas' child. 

- Robin Richmond 26 Sep 2016