User blog comment:Ajrep1994/Yang and Ruby are half sisters/@comment-5054402-20140724051121/@comment-11188061-20140724113835

That answer seems pretty serious to me. Exactly which part of,

'nice theory but no. Yang's her half sister. Summer Rose is Ruby's mother' sounds or reads like a joke to you? If it really was sarcasm he'd at least make some emotes or paraphrase it to make it obvious.

Besides, Monty has always answered these questions seriously. I don't see any reason why he would suddenly turn otherwise.