This project calls for putting the twin symbol ♊ in the suffix field, but it tends to create an error symbol in tree view. I began putting the ♊ symbol in the Display Name, and created a Label titled Twin, this way if someone does not like the display and ends up deleting it, the label Twin will be in the profile. I've noticed a few profiles that were NOT mine, but I edited to have the ♊ symbol, were deleted out, so as to not step on toes, I decided the Display Name was a better option, because the Red Alert error symbol bothers people.
Also the Label Twin can also have the ♊ symbol as well as you can name who the person is a twin of.