*nods* In this case, you can make it so publicly, they are Harkness-Jones, but in private, Jack can be "Mr. Jones-Harkness"...

You know, is it not possible to have Jack receive his real name as a gift from the Doctor? So maybe Jack forgot it, but it might be one of the greatest gifts he could receive, but keep it a secret from all others except Ianto... Or make it so it's actually IANTO that asks the Doctor to find-out Jack's real name as his gift to Jack... *nodnod eagerly*

... I hope I didn't confuse you... *shakes head* I'm confusing myself now... Will comment again when awake...