Since Meghan Markle began her relationship with Prince Harry in 2016, the actress’s older half-sister Samantha Grant has seemed like the loose cannon in the family.

So it was with some fanfare that A Current Affair announced an exclusive with Ms Grant, who was formerly in showbiz herself, on February 5.

“Is it the case of an evil stepsister or a big misunderstanding?” asked reporter Lauren Golman in her opening overview, before revealing Ms Grant’s partner keeps a loaded gun in every room of the rural Florida house.

The reality was a little less dramatic. Ms Grant, wheelchair bound for 10 years after developing multiple schlerosis, came off as mostly rational, if a little passive-aggressive.

While social media users slammed the interview as “immoral” and “bitter”, Ms Grant really only unloaded on Meghan, 36, in a mild voice to claim her family has woes including alcoholism and debt, and that Meghan has shirked her duty to help them out.

In particular, levelled Ms Grant, she hasn’t looked after the sisters’ father, former Married with Children lighting director Thomas Markle.

According to ACA, Mr Markle declared bankruptcy in 2016 and is now living in Mexico with as little as a couple of hundred dollars.

Why should Meghan have responsibility for her father, who won a Daytime Emmy in 2011? Because, said Ms Grant, he kickstarted Meghan’s acting career.

“I think he did help her a lot,” said Ms Grant, who nevertheless cut her sister some slack.

“She made the most of her environment. I don’t think he feels that she owes him, but that is how I see it.

“Honestly, you know, what she could spend in a weekend could help Dad. So that should be a priority,” said Ms Grant, who is yet to be invited to the royal wedding.

“If you can afford $75,000 for a dress, you can afford $75,000 to help your dad.”

Asked if Markle had “disappointed” her sister on that front, Ms Grant was unequivocal.

“Yeah,” she replied.

“I think you need to step up to the plate and make sure he’s well taken care of.”

Samantha (left) and Meghan in happier times.

Despite any perceived beef on Ms Grant’s side, she insisted (barring a plane falling on his house) that Mr Markle will walk his famous daughter down the aisle at St George’s Chapel, Windsor Castle, on May 19.

Ms Grant and her brother Tom are Mr Markle’s children from his first marriage. Meghan is from his second, to yoga teacher Doria Ragland.

When Meghan was born, “we became more of the complete family unit,” said Ms Grant, talking about their comfortable middle class Californian upbringing.

Old photos on ACA showed a younger Samantha with what she called a “Princess Diana haircut” hoisting toddler Meghan: “Meg was a lot of fun and I loved having her as a bouncing baby on my lap.

“I was always very proud of her. I never felt bitter or jealous.”

The sisters last spoke three years ago, and Ms Grant recalled: “The last words I heard from her were, ‘I love you babe, it was so great catching up and talking, let’s keep in touch’.”

She said Meghan, “got busy and I had to understand she’s all over the world with Suits, she’s busy in her social life.

“She was dealing with travelling the world and I never wanted to burden her.”

Ms Grant is trying to find a publisher for a book she’s written, The Diary of Princess Pushy’s Sister. She says the Pushy title comes from a headline she read about Meghan, not about her own thoughts of her sister.

Asked if she’s cashing in, she replied, “She probably thinks I’m cashing in. No, if I wanted to cash in I would go sue hundreds, even thousands, of publications who did stories using my name that I was not paid for and that I didn’t do.”

Desite Ms Grant’s best efforts, the interview copped flak online, with some viewers considering the exclusive a cheap move on the part of A Current Affair to capitalize on Markle’s post-engagement fame.

“This is rubbish journalism,” one Facebook user wrote. “Sensationalism. Garbage.”

“Why is @ACurrentAffair9 even airing this crap?” tweeted a disgruntled viewer.

“It’s giving this woman the publicity she wants. Ignore her and give Meghan the privacy she deserves.”