Abbreviate as Jr. and Sr. only with full names of persons or animals. Do not precede by a comma: Charles B. Luce Jr. The notation II or 2nd may be used if it is the individual’s preference.
Note: that II and 2nd are not necessarily the equivalent of junior—they often are used by a grandson or nephew.
If necessary to distinguish between father and son in second reference, use the elder Smith or the younger Smith. Also, see Roman numerals.