Jr., Sr., III

Jr. and Sr. are preceded and followed by comma in full name:

            John M. Fahey, Jr. (left), went to. . .

but     John Jr. hurried. . . .

No commas with Roman numeral attached to name:

            Nicholas DeVore III arrived.

For possessive add apostrophe plus s:

            John M. Fahey, Jr.'s memo

            Joel Bourne III's picture.