Re: Adding a middle name to a III or IV?
Technically, no, but given the human instinct for 'blast the rules' it's been commonly done through history. In my family we have a slew of Isaac's, Sr, Jr, and III in the 1700's and 1800's, each with a different mn - Isaac James, Isaac John, back to Isaac James.
So tell the relatives 'yes' you can, give your boy a mn and let them tack III on the end. Strict name etiquette pedants might argue that by adding a mn you altered it out of III mode but honestly, how many of them do you run into in your normal life ;o)
Devon