User blog comment:Samuelshadow16/Are Ruby and Yang Blood Related/@comment-14909251-20130929225810

This is what Oum has tweeted on the matter that I could find:

" @FortressSea: @montyoum So Ruby & Yang are sisters(I've heard)... But not blood related?"they are sisters. Like sister are sisters - 11:15 AM - 18 Jun 13

Why does everyone keep asking about Ruby and Yang's relationship? Would you rather watch the show? - 11:20 PM - 18 Jun 13

"@CurlyFreys: @montyoum Why do Ruby and Yang have different last names?" "It's a long story." - Yang - 1:33 AM - 4 Aug 13

He has neither confirmed nor denied a blood relation and the tweets could be taken any number of ways.