We grew up in a loving, middle-class Roman Catholic family in West Sussex, together with our younger brother, Charles.
Our father, Michael, worked as a contracts manager for an engineering firm; our mother, Jane, was an editor for Jane’s Defence books until she died five years ago.
We had a normal, happy childhood; there was never a great deal of money, but there was always plenty of love.
As a child, my sister was always sickly. She had pneumonia 13 times in two years; her lungs collapsed, and one of them never recovered.
Her kidneys also gave her problems, and when she became pregnant with the first of her three sons at the age of 22, one of them finally gave up altogether.
She’s now 36, and for the past 14 years, she’s limped along with a single fitfully functioning kidney, spending frequent spells in hospital.
We both know that she could lose the use of her remaining kidney at any time, condemning her to a lifetime of dialysis unless she finds a donor.
As her brother, I’d be her best bet for a genetic match.