I'm the sister and from time to time I too shall be logging on and giving my own two cents about what it was like to grow up with an aspie for a sister. Ever since she's been properly diagnosed all of those weird things she's said and done now make a whole world of sense. I have almost 5 years of experience working with kids from first grade to high school who have a wide range of special needs both physically and mentally, which allows me to look back and understand much better why it is my sister behaved or reacted the way she did in certain situations. If only we knew then what we know now. But because the use of Time Turners are heavily monitored by the Bureau of Magic (in the US it's the bureau not ministry), we don't have the ability to turn back time and correct the incidents that have made her life harder. What I hope to do is give little vignettes into our lives as kids and reflect on my reactions and discuss what I did or did not do and what would have been easier on my sister.
Of course, as a kid, when your sister is driving you crazy and you want to drive her crazy right back, you're not about to take her tweaked brain into account. No matter how much you might love her.