Spinster aunt. She raised you all and YOU'RE WELCOME, ingrates. You give a child a weird name one time and they feel entitled to bitch about it the rest of their lives, I swear.

Anyway on the subject of last names I vote that if they were deposited as a baby they get "aunt's" last name but if they arrived when they were older they can keep their original name and just get saddled with a vice "nickname."