Kate Middleton and Prince William, just recently, celebrated the duchess' birthday. Although she is just about to turn 38 on Jan. 9, which will be on Thursday, the royal couple seemed to choose a much earlier celebration.

On weekends, the Duke and Duchess of Cambridge headed to their royal country home at Anmer Hall. It was revealed that invited some of the "closest friends" as well as Kate's parents, Michael and Carole Middleton.

The activities that the couple spearheaded for their guests were revealed to be the "traditional" types that only the countryside can offer. This mainly includes "shooting," as per sources.

According to Express UK, the weekend "lavish bash" was a success. Despite the need for Kate Middleton and Prince William to return to London for their royal duties, it seemed like everything went well for everyone.

However, sources believe that the Duke of Cambridge has a lot more in store for his wife's birthday. As claimed, Prince William has been keeping a secret surprise getaway for Kate Middleton.

Based on statements released by various reports, the duke has been planning for their family to have a lavish getaway in Mustique. This was first released in December, and was believed to be an ideal choice given the "bumpy" year that the royal family had.

Cheat Sheet also released a few details about the reported surprise birthday bash. It was stated that Prince William wants to "whisk" the whole family away for a "no-expenses-spared" trip. It will be a "big surprise" for Kate Middleton, the source explained.

Upon arrival in Mustique, which was also revealed to be one of Prince George's and Princess Charlotte's favorite destinations, the Cambridge family will reportedly stay in a "$15 million, seven-bedroom mansion." The estate was also said to feature an infinity pool, screening room, tennis court, and a private chef.

Aside from the trip itself, the source further shared that Prince William plans to make everything "extra special" for Kate Middleton. So, he has planned a few "fun" activities for them including a surfing lesson, diving activity, and a spa session.

While these reported plans of the Duke of Cambridge will be very fun and suitable for the duchess, there have been no confirmations made about the matter. So, until Kate's birthday arrives this week, no one knows for sure what the couple's plans will be for the event.