Clarity

Had there ever been any instance in the show that Twi ever had siblings before A Canterlot Wedding?

So pony racism just goes in and out of fashion, just like that? So for our convenience, ponies just decide "let's not be assholes, for this small amount of time". You don't have to mention your brother.

So, if it hasn't been specifically shown to be false, it must be true?

XD okay, have fun with that mentality.