How do you know he doesn't? Just because he or his family never mentioned one to the public, doesn't mean he didn't have one. Y'all don't know everything about these rappers or their lives. And yes, that's really him on his twitter. So it isn't just a news source. We all know Nas isn't a really social type of dude (he's very introverted). So for him to say that is a major thing.
i saw thread & thought, "damn. i didnt know he had a sister" but i didnt jump to believe nor discredit it.
to them other dudes making it a big deal, he is only going off what was said on Twitter.
Yall probably think Jungle is Nas' only brother too