Here's a cute video I took of Sophie and Morgan a few weeks ago. I've tried to post it several times, but either blogger or YouTube would not cooperate.
Morgan absolutely loves her sister! She's not really a sweet kitty, except when it comes to Sophie. She tries to rub all over her and cuddle with her, and usually Sophie wants nothing to do with it, but she'll tolerate it - at least for a little while. Listen towards the end, and you can hear Morgan purring - not the most pretty purr, but I still think it's cute.