Could possibly be that you do have a twin, and don't know it. When my mother was pregnant of me, she said she was the biggest out of all four of her pregnancies. She was convinced that she was having twins. I was barely 6 lbs when I was born, and back in the day (50 years ago) the women were "put out" during child birth. 20 years later, my two brothers each told me that they had seen a young woman that looked exactly like me, one at a bar, and the other at the shopping mall. I didn't think a whole lot of it, but one day, still in my twenties, I was in a grocery store, and a man called out to me several times, but he was calling some other name and I just thought he was a little weird. He came up to me, looking shocked, he said, "I'm sorry, I thought you were my sister, you look just like her." He said, "I was wondering what she was doing here, because she lives in Arizona." I kinda laughed, and said, "My brothers have seen someone here in Albuquerque, who they thought looked like me, too." He said that his sister used to live here, but moved to Arizona several years ago. It was a litter eerie, and in retrospect, I probably should have looked into it further, but never did.