Bob -- It does not appear that Elijah was Wm's brother. However, Elijah may have been Wm's uncle.
Brothers of Elijah FLOYD (1798-1876) included
( ) David Jr (1786-1856) md Mary Magdalene REAGOR (1793-1856) -- 1830 USC (0111001-121001 ....Their son, David A, was bn ca 1820 ( ) Jno(ca 1784-POST 1828) md Mgt FINNEY -- ch Jas K (1806), Mary (1810), David A (!812), Spencer (1815) ( ) George md Annie COX ( ) Enoch md Anna Waters SHOOK ( ) Hosea Holcum md Elizabeth Ann COUSER
It would appear neither Elijah nor Jno FLOYD were Wm's father. If none of their brothers were, either, perhaps Wm was a grandson of one of their father's brothers
Sons of Enoch FLOYD Sr (1737-1795) and Mgt Jane MILTON (1737-unkn)
( )Jno FLOYD (1765-unkn) -- may have moved to IL ca 1829 ??) ( ) Enoch Jr (1767-1801) md Elizabeth NORMAN ( ) Nathaniel ( ) David Sr (ca 1765-pre 1828) md Jane NORMAN (their sons shown above, including Elijah and Jno) ( ) George ( ) Samuel (ca 1770-unkn) ( ) Aaron
I regret that I do not have add'l details on these men, but you might want to look into the family of David FLOYD, Jr and his wife, Mary M (nee REAGOR). The 1830 Census information implies they might have had a son born about the same time as your William. Good luck with your search. -- Jack