@whitequark some hoity toity folk who aren't Esquire or Junior might be the 3rd, 4th or 5th but may prefer to not use Roman numerals or spell it out is what I am thinking, and I some jurisdictions around the world allow it. All the systems I have worked with permit numbers for this reason. Here in Canada rules vary by province but generally require such names to use Roman numerals or spelled out in English or French.
Strangely enough although you cannot have Arabic numbers or non-roman alphabet characters in your government registered name you CAN have the following punctuation in your name in most of Canada:
! " # $ % & ’ ( ) * + , – . / : ; > = < ? [ ] \ ^ ` ´ ¸ @
Punctuation was permitted to allow more accurate representation of indigenous and foreign names within the constraints of the Roman alphabet.
Basically no system should make assumptions about names and they should really just use one big happy UTF8 field.