The heartwarming moment Kate Middleton kisses Prince Louis on his lips

This is so adorable!

The Duchess of Cambridge looked every inch the doting mother as she fussed over her three children at the King Power Royal Charity Polo Day on Wednesday. The 37-year-old was on hand to support husband Prince William at the game, which took place at Billingbear Polo Club in Berkshire. She was seen keeping a close eye on Prince Louis, while a cheerful Prince George and Princess Charlotte played on the grass. And there was one particularly sweet moment which didn't go unnoticed - Kate melted hearts across the globe when she was seen planting a kiss on little Louis.

The tender embrace was captured when sister-in-law Meghan stepped out of her car with little Archie in her arms - take a look on royal blog account, william_catherine82. Over the course of the event, Louis - who is almost 15 months old - kept his mum very busy. At one point, Kate was spotted running towards the horses as she dashed after him and scooped him up. He was also seen blowing kisses to his cousin Archie, whilst wearing Kate's sunglasses.

Prince Louis with little Archie on Wednesday

Prince William and Prince Harry played against each other in honour of Leicester City chairman Vichai Srivaddhanaprabha, who was an avid polo supporter and president of Ham Polo Club for four years. He was killed in a helicopter crash at the King Power football stadium in Leicester in October last year. The event marked the first time royal watchers got to see baby Archie with his cousins. Harry and Meghan's son was christened at a private service at Windsor Castle on Saturday.

GALLERY: Kate and Meghan unite with kids including baby Archie to watch Princes at polo

The charity match helped raise funds and awareness for more than 15 charities supported by the Dukes including African conservation organisations, rugby charities and the Invictus Games Foundation.

MORE: Who is inside Duchess Kate's inner circle?

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