Exactly this. Thank you. That thread made me sick. I  have little sisters as well. 12, and 13. I love them both more than anything. (I'm 23 and havent lived at home for a few years)

They come to me about things they dont tell my mom, nor my dad. Things about kids asking for pictures, questions about things kids would bring up in middle/elementary school settings. As weird and difficult as it was for me, to fight off the stereotypical mean scary older brother look. I'm really glad i did so. They trust me, and I cant put a price on that. 

 But I would never in a million years pretend they were old enough for toys. Ask any question, be curious. Like who you want to. But naw son its gonna be a hard yikes from me when it comes to the original AITA thread. OP was right. The internet is a scary place.