should I add a period and a comma after the middle name
No, they are not. Someone who is a Jr, can drop the Jr or even add Sr at the appropriate time, without recording it in the courts.
No, you do not add another period after "Jr." at the end of a sentence. The period after "Jr." serves as both an abbreviation marker and as the end of the sentence.
JR Reed's birth name is Jason "JR" Reed.
John Ross
To have a II (roman numeral 2 (two)) in a name will happen almost the same way someone is named with a jr. You get your fathers name and add jr. you get your grandfathers name and add II. If your father has the II already (like my father) you get your name to end with III (like in my name) after that the sequence is IV, V, VI (like star wars) VII, VIII, IX, X get more at this website.Roman NumeralsChart
JR Redwater's birth name is Dominic Duwayne Redwater Jr..
Bowser Jr's proper name is Bowser Jr. He is called "Junior" by his father, but his real name is Bowser Jr.
Lee Armstrong Jr's birth name is Lee Marshall Armstrong, Jr.
Steven Wothe Jr's birth name is Steven Gregory Wothe Jr..
Don Finklea Jr's birth name is Donald Ray Finklea Jr..
Fred Gaines Jr's birth name is Frederick Weller Gaines Jr..