Samantha Markle slams Duchess Meghan in series of scathing tweets defending father, Thomas Markle

Duchess Meghan's half-sister, Samantha Markle, said in a barrage of tweets this week that she would hold Meghan responsible should their father, Thomas Markle, pass away.

Samantha, who has been frequently outspoken against the former "Suits" actress since her relationship with Prince Harry became public, fired off several tweets from her private Twitter account in the days following Thomas' critical comments about Meghan and the rest of the royal family.

Along with a link to a story about Meghan and Harry paying tribute to Nelson Mandela earlier in the week, Samantha questioned why her half-sister would honor the late Mandela instead of Thomas, who said that the royal family "haven't had any contact" with him since he suddenly dropped out of the royal wedding in May.

"How about you pay tribute to your own father?!" Samantha tweeted. "Act like a humanitarian act like a woman! If our father dies I'm holding you responsible, Meg!"

"Glad you have so much time to gallivant around paying tribute to others while ignoring your own father!" read a subsequent tweet. "How cold can you be and look in the mirror? Harry? I guess I was right."

Thomas spoke to The Sun about his strained relationship with his daughter and posited that she's "terrified" in her new role as a royal.

"I see it in her eyes, I see it in her face and I see it in her smile," he explained. "I've seen her smile for years. I know her smile. I don't like the one I'm seeing now. This one isn't even a stage smile -- this is a pained smile. It really worries me. I think she's under too much pressure. There's a high price to pay to be married to that family."

In another interview with TMZ, Thomas called out the royal family for giving him the silent treatment because of his continued insistence on doing paid interviews about his famous daughter and her new family.

"I was silent for a full year and the press beat me up every day saying I was a hermit hiding in Mexico, so I gave my story," he said. "Apparently that interview [with Good Morning Britain] put the royal family in their silence mode ... so, I gave another interview to break the silence. All they have to do is speak to me. Tomorrow is my birthday, 74 years old, and I'm enjoying the fact that I can make the entire royal family not speak. And maybe I can get a laugh out of the duchess."

In one final tweet, Thomas' daughter, Samantha -- who has a different mother than Meghan -- continued to defend her father amid a continued public controversy surrounding him.

"My father is not an embarrassment for loving his daughter!" she added in another tweet. "The Royals are an embarrassment for being so cold. You should be ashamed of yourselves @KensingtonRoyal."