My dear Lana

Even though you knew from the age of 3 that babies could be born with cancer and that chemotherapy treatments weren't just for grown-ups, to discover at the age of 8 that children were also dying of cancer here in Switzerland, and that this was the case for your little sister, was not humane.

I've always believed that the role of a parent is to give love and protection to our children. But I realize that we haven't been able to protect you and your sister Zoé.

We couldn't protect your sister from illness and suffering. Nor could we protect you from the sadness and pain of losing your little sister.

For 5 years, our lives and yours have revolved around Zoé's treatment schedule.

I remember the day you asked me to take riding lessons. It was your dream. I told you in all honesty that we didn't know where your sister and I would be next week or in two months' time. At the CHUV in Lausanne or abroad for that treatment we were so hoping to do...

How do you plan activities when you don't even know where you'll be the next day?

During the illness, everything revolves around the sick child. This is the reality for families with a child battling cancer. And the siblings suffer the consequences. It's always been very painful for me to realize that, even though I've always loved you both equally, your wishes were more important than your sister's treatments.

I always thought that if I explained things to you, you'd understand, even though you're so young. But sometimes I wonder how you managed to never show jealousy towards your sister. So much attention on her and still today... people send us messages to say they're thinking of us at this time. But what about you? How many people are thinking of you at this time and the pain you're feeling?

Yet you were by your sister's side for five years. You were the one who encouraged her, loved her, cuddled her. And she adored you. You adored each other. You used to say to me: "She's so funny, I adore her." She was always clowning around, and you had invented a whole world for yourselves in the neighborhood. The neighborhood was a hospital for marine animals. In this green space was Winter's space, the dolphin Zoé dreamed of meeting. The neighbor's garden was the seal tank, and the field behind it the other dolphins' park.

As soon as the days got less sunny, the playmobile village took over, where you invented another world, where, of course, there was a hospital. That's when you started playing doctor. For as long as I can remember, you've always talked about working in the care sector.

From an early age, you helped me with the daily chores with your sister. You always asked lots of questions and wanted to participate. You helped me with Zoé's famous injections. You helped me disinfect and distract your sister while I injected the product. You watched as I tried to put down that damn pee bag to collect your sister's urine over 24 hours; you knew which button to press to turn off the pump that fed your sister and when it beeped. It came as no surprise to us when you chose to pursue your medical studies.

Today would have been Zoé's 15th birthday. We're sad because we miss her, but we miss her every day, not just in October. The traces of life with 4 are still there, but there are only three of us left at the table and we miss Zoé every day.

You agreed to "share" your little sister by agreeing to make our story public. Even if it's not always easy for you or for us.

There are malicious people who try to make our story their own, and others who criticize our choice to publicize our lives. You have to know how to deal with all that, and it's not easy every day. I know I can't always do it...

It hurts you and us, but we haven't forgotten all the beautiful messages we've received. People who thank us for daring to speak out, for sharing our experiences and for what it has done for their lives. People who are grateful for what we do, and who admire our ability to talk about our difficult lives.

Never forget that you are and always will be Zoé's big sister, the one she loved so much, the one she always asked for when we were in hospital, and that you are the person who has meant the most in her life.

It hurts me to see you suffer, because I'd like to have spared you this pain, or at least prevented you from discovering it at such a young age.

We don't "mourn" because we don't heal; there is no end. We survive, we learn to tame the absence and it becomes like a friend, a true friend who is always present at our side.

Seeing Zoé's school friends in the neighborhood growing up, imagining how your life would be with her by our side. Hearing others complain about their brother or sister when you had such a close bond must be difficult for you.

Sometimes I imagine how frustrated she would have been not to be able to accompany you on outings with your friends. She would certainly have found it hard to accept that you could go and have fun without her. I imagined her when you were 18 and graduating from high school. We were so proud of you, and Zoé would have been too, to know you were in medical school and to see you wandering the hospital corridors she'd visited so often. I can sometimes picture the two of you, driving around in your car, music blasting, to those songs she loved so much and that we still listen to.

I know you know that pain in your chest as if your heart is clenching, your throat closing, your eyes burning. You know these sensations and they still come back, even 10 years later.