The family as I track it is this.
ASA (Ace) Webb b:MARCH 1806 in TENNESSEE, D:SEP 1888 in JACKSON CO MISSOURI, married Mary Unknown Both buried in Webb Cemetary Jackson Co MO.
son William Webb b:DEC 1824 in TENNESSEE, D:FEB 1886 in JACKSON CO MISSOURI, married Mary Boyers b: 1850 MISSOURI
son William Oscar Webb b:1874 in MISSOURI, D:? married Mary Catherine Land b:1875 in MISSOURI
This tracks with the 1880 Census with William and Mary and son W.O. in Blue Township Jackson Co MO.
He is also noted in the 1850 Census living with his grandfather Joseph Webb (b:abt 1785) in Blue Township Jackson Co. MO
He is found living alone next door to the Rodgers clan in Blue Township, Jackson Co. MO in 1860 dwelling 641 close to father Asa Webb dwelling 665. Uncle Allen Webb (Asa's brother) is in dwelling 642 and cousin William Webb (who married an Elizabeth ?) is in Dwelling 643.
In 1870 census he is found living in the household of Winslow Rodgers in Independence, Blue Twshp, Jackson Co, MO.
RODE WITH THE MISSOURI PARTISAN RAIDERS WITH HIS BROTHER PRESTON WEBB LATER JOINED CALVARY UNDER SHELBY
BOTH WILLIAM AND HEWITT PRESTON PRESS WEBB ARE BURIED IN SALEM BAPTIST CHURCH CEMETERY SECTION 21, TOWNSHIP 50, RANGE 31W
ROSTER OF THE MISSOURI PARTISAN RAIDERS
http://www.rulen.com/partisan/roster.htm lists the date of death of Thomas B. Webb as November 1914 but investigation of death certificates indicates a Thomas Benton Webb b: June 1835 in Oak Grove MO died Nov 8 1914 at age 79 in Bates Co Missouri and is buried in Vinita Oklahoma however Thomas B. Webb b: July 3, 1839 (TN) son of Asa Webb (TN) died at age 89 on Oct 22, 1928 and is buried in Blue Springs MO.
Thus I believe of the partisan rangers William, Preston, and Thomas were all brothers. I've not tracked down George or Charles but I suspect they are closely related.
From the Provost Marshall Index:
Webb, George, Thomas, Hugh, and Joseph; Jackson County Are held as prisoner at the Military prison in Alton, IL. 11-22-1862 F 1413
Webb, Preston; Jackson Letter from prison stating desire to take Oath of Allegiance 1-07-1863 F 1413
Webb, William; Buchanan Letter stating property of William Webb was taken by U.S. troops 12-28-1861 F 1413
Webb, William; St. Louis Oath of Allegiance 7-08-1862 F 1413
Webb, William; St. Louis St. Louis Letter regarding sending his slave to Kentucky 4-13-1863 F 1413
Webb, William; St. Louis St. Louis Tried and convicted of violation of the oath of allegiance to the United States Government 4-10-1863 F 1413
William L. Webb's book "Battles and Biographies of Missourians" Published 1900 is available online in the UM digital library at:
Its fun reading and appears relatively accurate including a nice sectionof Quantrill's early years, Upton Hayes and others from Jackson County MO. He even nails John N Edwards writing down with "Sometimes his imagination is riotous, but his sentances are always graceful." (page 326)
It appears that the author may be related and may be the William Webb of Oregan County listed as 9 years old in the 1860 census.