User blog comment:Endor 66/Why do Ruby and Yang have different last names/@comment-186.188.68.63-20140226184818/@comment-3146930-20140227002437

He doesn't have the heart to say the truth to nobody, so he does have the heart to tell the truth to somebody? Double negatives are fun.

Anyway, pointing out the flaws of a theory allow the theory to be refined and fixed as more information becomes available. I already have an idea that I've posted below and on other pages that Yang and Ruby's mother never changed her name when she was married or she was never married to Yang and Ruby's father in the first place. Then when they got older, they were allowed to pick their surname with Yang picking her father's name and Ruby picking her mother's as they were each closer to their respective parent. This can somewhat be seen by Yang being like their father (as stated by Ruby), and the song Red like Roses II pointing to Ruby being close to her mother. Gold then shows that Yang was willing to try and be there for Ruby supposedly after her mother's death, so obviously they knew each other because no one would take on such a responsibility like that for a stranger, especially if her father had a gf/wife to act as a mother to Ruby.