An Uncanonical Relative is a common type of Mary Sue. This character claims to be related to a canon character, and thus worms her/his way into the story on the grounds that if their important family member is important, they must be, too. This is false -- it can assumed that most every canon character has parents or relations (or a creator in the case of some nonorganism characters) and they may not be important or even mentioned. Some Sues can accomplish this due to their Adaptable DNA, which allows their genetic code to change to match those of guardian figures.