Prince Harry and Meghan Markle
Prince Harry and Meghan Markle might invite Pippa Middleton to their royal wedding. Pictured: Prince Harry and Markle visit Reprezent 107.3FM on Jan. 9, 2018 in London. Getty Images/Chris Jackson

Prince Harry and Meghan Markle attended Pippa Middleton's wedding, so they might return the favor and invite her to their nuptials.

Pippa was Kate Middleton's bridesmaid when she married Prince William in 2011. She has developed a great friendship with the royals. In fact, some of them were present when she wed James Matthews in 2017.

According to royal commentator Richard Fitzwilliams, the Duchess of Cambridge's sister might receive an invite to Prince Harry and Markle's royal wedding. The couple had been invited to her big day, and Pippa will likely return the favor "if they know each other well."

He stressed that Prince Harry and the "Suits" actress are not obliged to invite Pippa or any expected guests. "The emphasis is on those they want to ask and those they know," he explained.

Meanwhile, Markle has not yet invited her own family to her big day. Her half-sister, Samantha Grant, recently expressed her disappointment and anger on social media because the couple invited complete strangers but not her own family. Grant believes that the Markles should be present at the royal wedding.

"We are getting [the] Markle Royal Coat of arms but not invited to the wedding?" Grant wrote. "And it's not only Meg who is 15th cousin to Harry. My brother and I are also. I was the first born Markle to my father. Exclude the markle's from this wedding would be highly inappropriate."

"At issue is not a matter of closeness as more than 1000 complete strangers are invited. Family is family. I have an uncle I have only seen once but I would never say he is not family because we are not close. Humanitarians move forward with love and kindness especially to Family," Grant added in another post.

Unlike Markle's relatives, however, Prince Harry has invited Princess Diana's family to their nuptials. According to Katie Nicholl, Prince Harry invited the "the entire Spencer clan." Earl Spencer, his two aunts, Lady Sarah McCorquodale and Lady Jane Fellowes, and all of his cousins will be attending the wedding.

"Harry has always kept in close touch with the Spencers and they have all received invitations," a family friend said. "Harry gets on well with his aunts and uncle and they have met Meghan. His cousins all have the golden ticket—an invite to the ceremony and reception and the evening party."