William Crosthwait's wife was Malinda Nugent(Newgent). Malinda's first husband was William Gum. On the 1850 census,two of their children, John Alexander Gum and Sarah Gum, are living with their mother Malinda and her second husband, William Crosthwait. Another son, William Norton Gum, married Margaret Ward in 1847 and lives in the Sulphur Springs district of Rutherford County, TN.
It seems likely that the mother of all of the Crosthwait children listed on the 1850 census with William and Malinda are Malinda's children, although I don't have averified marriage date.