MAUREEN CALLAHAN: How difficult it must have been for Harry to hear the sad news of Charles' cancer diagnosis from so far away. As he flies home, could this be the start of a heartwarming royal reconciliation?

If there was ever a chance for royal reconciliation, now is the time.

For all of Prince Harry's openly expressed doubts that there is no need for him in the royal family, that he is merely a 'spare', the deeply disturbing news of King Charles III's cancer diagnosis proves that nothing could be further from the truth.

Prince Harry is essential to his family, now like never before.

King Charles has said the door is always open for his youngest son. This is the perfect time for him to seize this opportunity.

Just a few weeks ago, his sister-in-law, the Princess of Wales, was admitted to hospital for a two-week stay after abdominal surgery.

This was accompanied by the news that Charles would undergo surgery for an enlarged prostate.

As we now know, the king's surgery revealed cancer in another, unspecified area.

The palace does not want to provide further details, but the hope is that the matter will be discovered early.

Yet this newly streamlined monarchy has suffered two major blows, with the most popular royals – a king who has been on the throne for just over a year and the future queen, the brightest star in her sign – having been taken out of commission.

William has canceled all his appointments to be with Kate while she recovers. Charles, who started treatment on Monday, has cleared his schedule. Camilla will certainly be by his side in the coming days and weeks.

It is a dark hour for the monarchy – and undoubtedly a darker hour for Harry.

How hard it must have been for him to hear this sad news when he was so far away.

How keenly his absence, and that of little Archie and Lilibet, must be felt at home. Charles only met Lilibet once, during the Queen's belated Platinum Jubilee celebrations – the only time she also met her namesake.

“It was great to have [the grandchildren] back in Britain,” a royal source said at the time, adding that Charles and Camilla were “absolutely excited to see them.”

The palace has confirmed that Charles personally told each of his sons about his diagnosis. Harry announced that he is flying to London immediately.

Will his children soon join him, as the king and queen would surely hope? You feel that even Meghan can be welcomed gently. Charles finally walked her down the aisle.

William, as we know, is less forgiving than his father. But now that Kate is recovering, with three small children needing his constant presence, with an ailing father and the weight of the Crown suddenly heavier than ever, the absence of his only sibling must be painful again.

Could this window, long closed to Harry, be ajar?

What an opportunity this could be. What a comforting presence Harry and his children were able to provide to the King while he underwent treatment.

What a gift he and William could give their ailing father if they could find a path to rapprochement.

Of course, their relationship will never be the same, but that could be a good thing, or at least more honest.

A reconciliation does not mean that they have to go deep. If they can find a way to get back together, it would be bigger than any title, castle or inheritance – especially for their children, who are not related as cousins. And specifically for Harry's children, who have little relation to their most incredible and historic origins.

A fraternal reconciliation would secure the future of the monarchy itself.

Will Harry now find new appreciation for his blood ties with a wounded father who continues to protect him, a brother who shared with him the very public loss of a beloved mother, and indeed a sister-in-law that he once was? openly worshipped?

Harry failed to make amends with the queen before she died. He ultimately missed his chance to fly to her bedside with William and other family members after reportedly demanding Meghan accompany him.

You can imagine that he regrets that.

Harry's demand left the royal family “shocked by his behavior,” as Robert Jobson reported in his well-researched biography “Our King: Charles III.”

Jobson also claimed that stripping Harry of his title had been 'discussed at the highest level', with Charles refusing to consider it out of 'abiding love for his son'.

There has never been a more opportune time for a royal reconciliation than now.

Prince Harry is not only needed at this time. It is clear that he is highly sought after.

Let's hope the self-proclaimed reserve realizes how important he is – and all he can be, to his family and his country, if he lets him.