Ok ... what a mess !!!
Dad : the IRS already has a return with his SS# on it so he needs to mail in a return with the word "SUPERCEDE" on the top of the form 1040 and I suggest it be in BIG RED LETTERS ... use a sharpie if you have one. An amended return is not really the way to go since the entire return needs to be corrected and not just one item. Any refunds already received should be listed on Sch 3 line 12D.
Son : since no return was filed under his SS# then he can still efile an original return.
