Hey GM, I know if I use Tom and Jerry, respectively. I must use a comma behind Jerry. Do I need a comma
behind, "They are 11 and 2 years old respectively.
I don't think I need it but wanted to check. Can you
help? Thanks, William

There is very little written on this. Given that 'respectively' is an adverb which, above all, modifies a verb which usually appears earlier in the sentence, it is not necessary to use a comma at all. However, for ease of reading, a comma is appropriate.

I judge there to be a lot of leniency on this subject, and you should use a comma if you think it assists in making the sentence clearer.

Sorry, no ruling on this one.

Thanks GM.