You know what I never understood about the twilight fanfictions with renesmee having a twin. In most of them that twin gets abused because they thought that they were having one child. But how would they possible know that if, ultra sounds wouldn't work on Bella. So they could have been having freaking 3-4 children. So it wouldn't make sense for them to abuse that twin because they really didn't know what was going on inside of Bella's womb.