Sometimes physical addresses are even 0 letters from each other!
In my (distant) family, there was a guy who married a woman whose name was the same as his sister's, and she changed her family name to his. They all lived together for a short while.
Letters addressed to his wife and his sister would have the exact same address and exact same name on them, with no way to distinguish who the letter was for.
One more edge case to add to the "falsehoods programmers believe about names" list.
My brother and I have the same initial letter, same problem, but it was possible to use the first two letters as initial with some services. But in practice my mom would open letters to see who it was for, lol.
