MAUREEN CALLAHAN: The sad truth is that even Kate's cancer won't spark a Sussex ... trends now

Will Kate Middleton's cancer diagnosis finally smack some sense, some decorum and humility, into House Sussex?

Don't bet on it.

On Friday, hours after the Princess of Wales released her video message to the world, Harry and Meghan issued a statement from Montecito.

Loving and expansive it was not.

'We wish health and healing for Kate and the family' — not William by name, nor young George, Charlotte, and Louis — 'and hope they are able to do so privately and in peace'.

Compared to King Charles's effusive pride for his 'beloved daughter-in-law' and her 'courage' in going public, this feels… lacking.

Where was the sense of familial love – or anything remotely personal about the woman Harry once called 'the big sister I never had'?

Just one emotionally stingy, generically boilerplate line. From two people never short of words to describe their complaints.

Doubtless there was grievance behind this statement.

After all, the Duke and Duchess reportedly learned the terrible news about Kate along with the rest of us.

'They had no idea,' a source told the New York Post.

Of course not! It seems the only people surprised by that are the Sussexes themselves.

Following their bloodless statement came another colossal misstep, the news that Harry and Meghan had privately reached out to Kate on Friday night.

Is it really a private gesture if the world's media has subsequently been notified?

These two just cannot get out of their own way. If they had any hope of rebuilding an iota of trust with Kate and William, none of us would ever have known of these 'private' messages.

Harry and Meghan, despite cawing relentlessly about the intrusive media — of which they are a part, what with Netflix and podcasts and book deals and a pending cooking show and countless interviews and speeches — have zero concept of discretion.

They remain incapable, despite this gravest of moments, to realize when a story has nothing to do with them.

Or when it might serve everyone, their ailing sister-in-law and her small children especially, for them to keep their mouths shut.

Not such a big ask, is it?

As ever, it seems that this was all meant to redound to Harry and Meghan's benefit.

We are to understand that despite their most serious estrangement, they are both still in regular contact with the future King and Queen.

Please. As if Kate and William don't screen their calls and messages.

According to reports in the Telegraph this weekend, the Waleses have now put the so-called 'Harry problem' well behind them — note that dismissive description, as if Harry is a gnat, Meghan not even mentioned — especially as King Charles, too, is battling cancer.

What else, really, could the Sussexes expect?