Board Thread:General Discussion/@comment-24.95.92.0-20131114234400/@comment-69.114.227.142-20131116123901

A theory I saw may be the answer:

-Summer Rose and a certain unkown male are the parents of Yang and Ruby

-Ruby's last name WAS Xiao Long

-Ruby changed her last name to Rose after Summer Rose died

An idea that I came up with is that due to the culture of the area/family tradition, the last name changes from sibling to sibling based upon who was born first (Yang was born first, so her last name is Xiao Long and since Ruby was born second, her last name is Rose). However, this is probably not the case because it would seem weird if there are more than 2-3 siblings in a family.