By Tory Milne
BBC News Online Staff
There is not a single day of my life that I can remember when I haven't thought of Clare at least once. She is always there, in my mind, lurking somewhere, perhaps kept there by responsibility, or guilt, or affection; probably all three.
Clare, left, age 5, and me, age 6
She needs to be thought about a lot, because caring for Clare is a very complex thing.
She has Rett Syndrome, a genetic disorder which means, for her at least, that she can't walk, talk or look after herself in any way.
When people ask what she's like, I always tell them to think of a very young baby - and that's her, all of it, including the innocent laughter, unconditional love, and the demands made on those around her.
I'm 24, and she is nearly 23, and my only sibling.
Although she now lives in residential care, she lived at home with us right up until three years ago.
My childhood was largely defined by key moments in her life.
Her health needs led to regular hospital visits and stays, and, being only 21 months older, I always went along.
She had a tricky operation aged eight to correct a severe scoliosis (bent spine), and I vividly remember trying desperately to do my homework and go to school as normal, but being painfully aware that both my parents were in London keeping a vigil by her bedside.
I wanted to be with them.
What is Rett Syndrome?
A neurological disorder often misdiagnosed as autism
It is caused by a defective gene, found on the X chromosome and occurs almost exclusively in females
Development seems normal until between six and 18 months, when acquired skills are gradually lost
Additional problems can include seizures, breathing problems, problems with circulation, stiff muscles and curvature of the spine
Getting out of the house to go shopping, swimming, or even to go to school, was like mobilising an army.
Trying to find accessible parking for our specially adapted car was also a challenge, due to a seemingly massive desire by able residents in our town to park in disabled spaces.
Mum and I once gleefully took our revenge on a particularly large and ostentatious car by sticking about 30 "This is a disabled parking space. Please don't park in my space" post-its all over it.
Eating out was also a challenge.
Aware that other diners might find Clare's dribbling rather off-putting, we often resorted to fast food outlets, where other people ate with their fingers and made a mess.
Luckily, Clare is a huge fan of hamburgers and large numbers of screaming children.
Taking holidays with her when she was little was fine, but once she began to grow up, things got nasty.
Our last holiday as a complete family ended with both my parents lying on their backs on ice packs, in agony after days of lifting her weight up steps and into the bath took their toll.
We waited for hours for a district nurse to come and rescue us.
We've taken separate holidays ever since, with Clare staying at home with a carer - except for some lovely holidays to disabled friendly theme parks, still the only place where we feel 'advantaged' as a family.
Expecting a crisis
It is a family joke that Clare has an extremely finely-tuned sense of timing.
After one separate holiday in Yorkshire, my parents and I returned to find Clare in the grip of pneumonia. On a Nile cruise, we were called out of dinner to answer an emergency satellite call from her carer.
We never take plans for granted.
People often assume that I felt jealous of the attention she received when I was growing up. I wasn't. If anything, my parents overcompensated, cushioning me from the outside world in a way that rather frustrated me as a teenager, when I wanted to exercise my right to rebellion.
I don't live at home now, and neither does Clare, so life with her as an adult is rather different.
Clare and I still have a special bond
I feel guilty about not seeing her often enough. And when I think about her, it is often about her health.
A difficult future
Rett Syndrome is technically life shortening, and she does seem to be getting weaker. When she is in pain, we all ache to help her, but with no communication possible, making her better is a guessing game.
Still, thinking of her also brings with it some wonderful things. She is the one true innocent I know, and she can be depended on to be a great confidante, and a perfect solace in troubled times.
And whether or not she remains with me for years to come, I have a feeling she will be in my thoughts daily for the rest of my life.