Meghan Markle's half-sister Samantha wished the duchess a happy birthday on Twitter alongside a snide reminder to send a belated birthday card to their father Thomas.
The newly-minted royal celebrated her 37th birthday yesterday, on Saturday August 4 - her first since tying the knot with Prince Harry in May, according to the Daily Mail.
Meghan's notoriously outspoken half-sister sent her regards on Twitter just a few minutes before midnight in the UK, writing: "Happy Birthday Meg! It would be so lovely and appropriate of you to send DAD a BELATED birthday card for his July 18th [cake emoji] @KensingtonRoyal Cheers!"
Around the time of Thomas Markle's 74th birthday, reports emerged that the reclusive former Hollywood lighting director hadn't spoken to his daughter in at least two months.
Thomas has spoken about the estrangement in several interviews during that time, telling TMZ last month that he will continue talking to the media until he hears from Meghan.
Samantha has been her father's most ardent defender, sharing numerous unkind remarks about her half-sibling both in media interviews and on her private Twitter account.
In July the 53-year-old - who recently changed her surname from Grant to Markle - went on a Twitter tirade telling Meghan if Thomas dies "it's on you".
She launched another attack earlier on Friday, accusing Meghan of being cold to the family since marrying into the Windsor clan.
Samantha shared an article on Twitter that claimed the Duke and Duchess of Sussex were "taking a step away from the media spotlight", writing: "OK so Cruella de Vil is retreating LOL.
"Let me know how that works out for you."
Two years earlier in 2014, Markle also expressed happiness on her website, writing: "I am 33 years old today. And I am happy. And I say that so plainly because, well…it takes time. To be happy. To figure out how to be kind to yourself. To not just choose that happiness, but to feel it.
"So for my birthday, here's what I would like as a gift: I want you to be kind to yourself. I want you to challenge yourself.
"I want you to stop gossiping, to try a food that scares you, to buy a coffee for someone just because, to tell someone you love them…and then to tell yourself right back. I want you to find your happiness."