Meghan Markle's sister publicly blasts Prince Harry just a month before the Royal wedding

Her tough words seemed like a declaration of war on the ideals of the monarchical family.

As reported in an article published by Daily Mail, Meghan Markle's estranged half-sister, Samantha Grant, took to social media to target Prince Harry for allowing Markle to ignore her family members.

Grant believed that Harry's humanitarian causes get nullified if he is not even capable of handling familial relationships. The 53-year-old Grant accused Harry of being hypocritical.

Grant's tweet came as Markle was about to mark her first event as a Royal Family member when she joined Harry for a Commonwealth reception in London.

Before the social media post, Grant had put up a childhood photo of herself along with Markle as her profile picture. She replaced the nostalgic photo with one of her own images.

Grant wrote targeting Harry that it was time for him to 'man up' and disallow Markle to 'ignore the Markles.' She had previously criticized Markle for inviting complete strangers at her wedding instead of her relatives.

She accused that Harry and Markle were failing to honor proper tradition and etiquette. Grant had posted last week on her social media account that Markle should do the right thing and invite her entire family at the wedding.

Prince Harry and Markle are set to get married on May 19 at St. George's Chapel, Windsor Castle. The venue is the same church where Prince Harry was christened when he was three months old, according to The Sun UK.

St. George's Chapel can accommodate around 800 guests while the Abbey has 2,000 seats. Harry and Markle have invited an additional 1,00 members of the public who have excelled in humanitarian causes.

Grant, her brother, Thomas Markle Jr., his former wife Tracy and their children, Thomas and Tyler Dooley, were not invited to the wedding.