Harry's VERY Unhappy 40th Birthday Secrets Exposed: 'Spare Heir Mired in Misery' and 'Lonely' — and 'Won't be Getting Cake From Cancer-Hit Dad Charles'

Prince Harry will be celebrating his 40th birthday with his wife and kids at his home in California – away from the rest of the royal family.

RadarOnline.com can reveal he is unlikely to get birthday greetings or gushing tributes online from his dad and brother as he has alienated them with his antics, including his memoir.

The royal expert, who has known the prince since childhood, said: "Maybe he'll feel some sorrow at the way things have turned out, but he'll never admit that any of it was his fault."

Some in royal circles admit the Palace didn't handle the whole "Sussex situation" terribly well – while also strongly emphasizing how hard it has been to help a couple who make everything so "exhaustingly difficult".

The situation got so bad many within the royal's inner circle believed leaving Britain was the right thing for the prince to do.

One insider claimed: "He wasn't happy, he couldn't hide that, and he needed to make a break. It was a horrible, toxic atmosphere."

According to The Mirror, Prince William won't make a birthday call to his younger brother.

An insider claimed: "The relationship [between the brothers] is non-existent. William feels betrayed and has other priorities."

Even Harry's most loyal supporters agree the brothers' relationship is "complicated".

The source theorized: "I'd still like to think they might talk one day. But there's a long road ahead, and we certainly aren't any closer to that today."

Another insider close to Harry revealed the prince has become increasingly isolated and currently considers his security guard, David "Langers" Langdown, his best friend.

Some friends close to the Duke of Sussex are optimistic about Harry visiting the UK more often.

One source revealed: "He has various touch points in the UK, a handful of charities such as WellChild, and the Invictus Games, which will come to Birmingham in a few years time."

"There will be more reasons and requirements [for him] to visit, and the easier that can be done, the better. It's not a satisfactory situation at the moment, for all sorts of reasons."

The insider admitted Harry visiting his father, King Charles, is "more tricky."

"The UK is his home, it's where he grew up, it's where his family and friends and a lot of his interests are", they explained. "The sense I get is that there is a desire for some kind of rapprochement. Clearly, that will take time and patience. Let's just say there's a hope there will be more positive conversations in the future."

Prince Harry stressed the importance of family by telling People: "The greatest gift I've ever been given is, without doubt, my kids. I enjoy watching them grow every single day."

The distant royal is planning a small party at his $11 million Montecito home with Meghan Markle and their two children, Prince Archie and Princess Lilibet, followed reportedly by an outing with a group of his closest friends.

Of the family he left behind in Britain, it is unlikely that any of the other royals will be in attendance.

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