I knew there was something about you that reminded me of my (Muslim) brother. Like him you are having to deal with an apostate sibling.
ps I love my brother, dearly as I'm sure your sister loves you.
I wonder if thats what I see in him too - you know what, he's exactly like my brother was a couple of years ago, and uncannily enough says the same things.
He had disregarded the hadith, loved sci-fi movies and talking about the universe and was bored with Mullahs.
Only difference is that my brother questioned why I believed Allah had to be a nice & self-centric God and would always question why I felt Allah had to be given human characteristics.
He is now a deist because he cant get his head round the first cause, but still has a soft touch for Islam. My other 2 siblings still take the piss out of him for being a TP (typical pakistani) so its all good in the hood.