Fingers grow. That would cut off blood supply and teh finger would get gangrene.This twin discussion reminded me of a girl I met in college. She was a twin from some hoity-toity family in Bonn, Germany. Because the family was so hoity-toity, they had to pick an heir when she and her sister were born and they picked her (which of course she hated) but the thing that stuck with me was what they did to signify that she was the heir (and why she couldn't just give the heir-ness to her sister); they put a tiny gold ring on one of her pinky fingers and then broke the finger so the ring would be permanently stuck on her finger.
Guys who wear rings and use drill presses get their ingers messed up. ER's have saws they use to cut the rings off.
If you saw the finger and the ring with your own eyes, I will believe you, but if you didn't, I call urban myth.. or a grim fairy tale..