And while they have shied away from sharing updates on social media with their fans, the pair made an exception on Sunday as they celebrated a very special occasion.
Nicola, 27, decided to post a sweet new photo on her Instagram Stories, showing her posing with Harper Beckham in honour of her 11th birthday.
Alongside the filtered photo, Nicola sweetly wrote: "Happy birthday angel girl. I miss my little sis."
Brooklyn, 23, also took to Instagram to mark Harper's special day. He shared four throwback photos showing her through the years and wrote: "Happy 11th birthday Harper xx can not believe you are so old now. Love you so much xx."
Of course, Harper's proud parents David and Victoria also posted sweet tributes to their little girl. David, 47, shared a throwback video of Harper at bedtime, which he captioned: "Happy Birthday to my Pretty Lady. 11 years old today I can't believe it. You are the most beautiful little girl with the biggest Heart. we love you so so so much. Love Daddy [love heart]."
Victoria, meanwhile, shared three recent photos of the 11-year-old and wrote: "Happy 11th Birthday to our little everything!! The sweetest kindest most beautiful soul we could ever wish for [love hearts]. we all love you so much! X."
Nicola and Brooklyn tied the knot on 9 April 2022, at her father Nelson Peltz's impressive home in Palm Beach, Florida, estimated to be worth a whopping $103 million (£76 million).
Nicola is incredibly close to her parents – and it was recently revealed that her family have joined the couple on their honeymoon.
Nelson and Claudia Peltz were pictured enjoying a lavish yacht trip in a photo shared by their son Will, who also shared a snapshot of Nicola and Brooklyn enjoying the same view.
Taking to his Instagram Stories, the 36-year-old captured his sister looking more relaxed than ever as she sat with Brooklyn and other close friends and family around a table on a luxury yacht.
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