I need help processing this shit

So the other day I had to go through some paperwork about college and my my drops the most biggest fucking bomb ever. Turns out I have a pair of younger twin siblings (fraternal twins boy and girl) from my bio dads side that I never knew, my mom said it so casually and I just froze staring at her in disbelief. She 100% believed that she told me before but I would have definitely remembered that shit?!!! Like WTF?!!! I'm 18 and their fucking 16, SIXTEEN!!! Idk how to feel about this, I can't talk about this to my fucking family nor do I have any friends to even process this with!!! One part of me wants to meet them but like what if they reject me?? Or don't even believe it. Like "oh hi I'm your long lost older sister from your dad who had a one night stand with my mom nice to meet you!!" I wouldn't even believe that shit if I just randomly got that, Like WHAT DO I EVEN SAY TO THEM??! That I didn't know they even existed for pretty much my whole ass life until NOW?!!! Bro what is with this Wattpad ass shit