JANE GREEN: I know what my cancer did to my husband - and my heart shatters for William. After the devastation of Diana's death, Harry estranged, Charles sick, and now Kate's shock diagnosis - how utterly alone he must feel

Finally, the world can stop speculating, coming up with numerous fantastical conspiracy theories, or tasteless 'jokes' about what has happened to Kate Middleton.

I'm sure there are plenty of people who felt ashamed of themselves as news broke Friday of her cancer diagnosis. But the one person I'm thinking about in all this, the one person my heart goes out to in every way, is Prince William.

This poor man.

From his parents' separation when he was only ten years old, to their subsequent divorce, followed swiftly by his adoring, adored mother's untimely death, we have continued to witness life throwing hardships at him, over and over.

In more recent years, he's weathered mounting discord with his only sibling Harry and sister-in-law Meghan, his father's cancer, and now this – an unexpected and tragic burden on top of everything else.

Undoubtedly, the distance with Harry is felt particularly keenly.

The one person I'm thinking about in all this, the one person my heart goes out to in every way, is William. From his parents' separation when he was only ten years old, to their subsequent divorce, followed swiftly by his mother's untimely death, we have continued to witness life throwing hardships at him, over and over. (Pictured: Harry and William with Diana).

In more recent years, he's weathered mounting discord with his only sibling Harry and sister-in-law Meghan, most recently his father's cancer, and now this - an unexpected and tragic burden on top of everything else.

After all, he is the only person who might fully understand what this is like. The only person who also endured both divorce and the death of a parent, in such a devastatingly public setting, is irreconcilably estranged.

Surely too many rocks have been thrown, too much hurt, too much wounding for Harry to offer any solace or strength to William.

William who is now wearing the weight of the crown as his 75-year-old father undergoes his own treatment for cancer; William who must support his young family as never before.

As someone who has danced with cancer myself, I know how overwhelming it is for your partner. My husband was terrified when I received my diagnosis of malignant melanoma in 2014, far more terrified, he later told me, than I appeared to be.

Our children were 14, 13, and the twins were 11. While everyone rallied around me, few thought to check in with my husband. 

He stepped in to look after the children, to drive them back and forth, to ensure their lives continued as normal, all the while worrying about what might happen to me. 

When friends would phone him, they would ask after me, and he, like William, shouldered much of the burden alone, putting on a brave face, knowing he had to be strong for us all.

We now know that the prince pulled out of his godfather King Constantine's memorial service at the 11th hour last month because he'd just learned of Kate's cancer. Two days later, he was back to work, showing enormous bravery and commitment to duty.

We will be hearing endless speculation about Kate in the coming days, but few think about the partners and all they have to endure when their beloved is struck by serious illness.

William's pain right now is even more profound given his three young children: George, 10, Charlotte, 8, and Louis, just 5.

They are not much younger than William was when his mother passed, and that trauma and grief, the specific fear of losing a mother, is no doubt something he will bend heaven and Earth to shield them from.

We do not have a prognosis for Kate. She tells us she's undergoing preventative chemotherapy, that she feels 'well' and is 'getting stronger every day.' We are all thinking of her and praying.

But illness is a great leveller.

Undoubtedly, the distance with Harry is felt particularly keenly. After all, he is the only person who might fully understand what this is like. The only person who also endured both divorce and the death of a parent, in such a devastatingly public setting, is irreconcilably estranged.

Surely too many rocks have been thrown, too much hurt, too much wounding for Harry to offer any solace or strength to William.

William's pain right now is even more profound given his three young children: George, 10, Charlotte, 8, and Louis, just 5. They are not much younger than William was when his mother passed, and that trauma and grief, the specific fear of losing a mother, is no doubt something he will bend heaven and Earth to shield them from.

Irrespective of however much help the Waleses may have, however many nannies or on-duty nurses, William now must be a staid force of fortitude for his children and wife.

And while Kate may need space to break down, to lie awake at night as fears dance around her head, William will feel he has to be a rock, as all partners must when their loved ones are so seriously stricken.

This is William's struggle as much as it is Kate's, but he, as stoic and gracious in public as his mother always was, will now be under pressure to keep that mask on at home, too.

However terrified he may be, he isn't allowed to show it.

He has to keep smiling for the children, reassuring them that everything will be fine for Mummy.

Children are remarkably perceptive – if he allows his fears to surface, they will pick up on it, so he must keep it all buried deep as he surrounds them with the safety, security and love they need right now. 

He's not just a husband, a father, and a prince; his primary role right now is caregiver.

Whatever it is your life revolved around – family, work, charities, royal garden parties – everything stops as hospitals and doctors take over your everyday.

Given everything William has gone through in life, we can only hope that he does have trusted friends and loved ones who are looking out for him as well.

They must let him know that as stoic as he might need to be for Kate and their kids, he must know that he is allowed to crack, to let that scared fifteen-year-old boy, who just lost his mother, out.