As August approaches, the royal family's engagements are starting to slow down, with the Cambridges already reported to be enjoying a holiday in Mustique.

The Duke and Duchess of Cambridge, Prince George, Princess Charlotte, and Prince Louis were spotted making their way to the private Caribbean island of Mustique, royal blogger Tea Time with the Cambridges pointed out earlier this month. But we could be seeing the Duke and Duchess back on home ground a little sooner than expected.

The couple are thought to be returning to the UK this week, in time to watch their friend, Charlie van Straubenzee, marry Daisy Jenks in Surrey on Saturday.

Celebrities Attend Wimbledonpinterest
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William and Kate were last seen in public at the Wimbledon 2018 final

Prince William and Prince Harry became close with Charlie and his older brother, Thomas, after they met at Ludgrove Prep School as children, HELLO! reports. They have remained friends ever since, and Thomas is now godfather to Princess Charlotte.

The bride, Daisy, who works as a videographer, is also thought to have grown close to the royals over the years and was pictured in the congregation at Harry and Meghan's wedding ceremony in May.

Charlie van Straubenzee and Daisy Jenks pictured in London in 2017pinterest
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Charlie van Straubenzee and Daisy Jenks pictured in London in 2017

But the wedding isn't the only occasion that might bring the royals together on Saturday. It's the Duchess of Sussex's 37th birthday, and with Meghan and Harry also tipped to attend the nuptials, the royal couples might even get to celebrate together.

According to royal photographer, Tim Rooke, Prince Harry is lined up to be best man this weekend.

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'Unfortunately I will be missing the wedding of Charlie Van Straubenzee and Daisy Jenks where Prince Harry will be best man on August 4th in Churt, Surrey as I will be on the beach. Can't do everything,' he wrote on Twitter.

We'll have to wait until Saturday to find out if Meghan, along with William and Kate, are at the big day, although it wouldn't be the first time she has attended a wedding this summer. She joined Harry at his cousin Celia McCorquodale's ceremony in June, when Celia married George Woodhouse at a small church in Lincolnshire.

Kate Middleton and Meghan Markle at Wimbledonpinterest
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Kate and Meghan attended Wimbledon together

Meghan wore a blue and white floral Oscar de la Renta floor-length wrap dress for the occasion. No doubt all eyes will be on her latest wedding guest - and birthday girl - style this weekend.