Good luck Fizz!
Hope the volunteer feels better soon Tiny, sounds serious 
My younger sister and I are 14 months apart Kitty. It took six years to conceive me after my older sister so mum and dad thought they better start trying straight away 
It was hard work for mum at first but we were inseparable when little and we played together. She slept in my bed for years (she had childhood epilepsy and really bad nightmares). When she was older I was the person she'd wake when having nosebleeds (again epilepsy related) and we were mistaken for twins a lot.
We grew apart as teenagers as we got tired of being in each others' space all the time. We fought a lot, but now, as adults, we're still very close. I got her a job at my company when she left uni and we ate lunch together nearly every day. We teach together at music school and everything.
I love my older sister too but it's a different type of relationship. She's very much the eldest and it's taken til we were adults for us to be friends. No 12-year-old I know wants a six-year-old trying to play with them and their friends!