I've known two people in my life who went by some version of Trey as a nickname, as in some slight change if tres, three.

Or 3 James was confusing so they probably had a James, a Jim, a JT. No attempt to obscure just trying to yell at a specific person when the trash needs to be taken out.

I know a lot of people that just go by their middle names in this scenario. Even my brother was named like this and the intent from the beginning was he’d go by his middle name.

I think maximum pompousness goes to those that make sure you know they’re a third or fourth. If I meet you at a cocktail party and will never meet you again, don’t introduce yourself as William H Gates the Third, just say Bill.