‘No, I can’t do that’ is because we haven’t really practiced doing that.

That’s what we’re here for :) This one’s not staying in the bucket. Share it with her, Ganesh!
I’ve got trouble expressing affection to members of family as well. I’m about to clear that with mom & dad, but the work’s still pending with my younger brother (In 4th year col.) So I’m gonna start a post from yours soon. But for now, and this is powerfully weird, share this to your sister & when you’re done talking & laughing, TELL her ‘I’d like to give you a hug.’ ( I plan to do the same way too.) 
It’ll be over quick, and you’ll wonder what’s been the big deal so far. Make a memory!