I'm the great great granddaughter of David Boyle (Jr). From my research, he and Margaretta had three children (that I know of): Mary Agnes (b. 1868 Demopolis, Marengo Co. AL), William Albert (b. abt 1872 in CA), and Henry James (b. abt 1870 in CA).
Mary Agnes married Charles Russell Smith (who was from IL) 11 Apr 1896 in Chicago and lived with him in the Chicago area. They had several children, one of which was my grandfather, David Boyle Smith (b. 25 July 1900, Cook Co, IL; d. 26 July 1950 Ontario, CA). If you wish more information, please feel free to contact me.