User blog comment:Derrmann/By Jove, I've got it! (Totally know why Ruby and Yang have different last names)/@comment-4010415-20131116065346

Blood-related: https://twitter.com/montyoum/status/399672622935314432

Not step-sisters: https://twitter.com/montyoum/status/399673609204940800

Not cousins: https://twitter.com/montyoum/status/399678967881289729

Can't remember where to find the tweet where Monty said that he never said they weren't sisters.