Princess Charlotte spotted out with mum Kate and newborn baby brother Prince Louis

Princess Charlotte is proving to be taking her big sister duties very seriously, as she was spotted spending time with her mum and new baby brother Prince Louis.

The three-year-old became a big sister last month when Prince Louis was born, and reports have since suggested that she won’t leave baby Louis’s side.

According to Vanity Fair's royal correspondent Katie Nicholl, the Duchess of Cambridge - who only gave birth three weeks ago - was spotted spending some time outside at Kensington Park Gardens on Tuesday afternoon with her new baby and the little princess.

Kate is said to have been walking Louis in an 'old-fashioned pram', which is reportedly the same she bought when Prince George was born in 2013 - a luxurious Silver Cross baby carriage.

The three royals were accompanied by the nanny, Maria Borrallo, and despite not having been noticed by photographers or paparazzi, they were accompanied by three protection officers.

Princess Charlotte, who was pictured on her birthday having a sweet moment with her newest sibling, was apparently enjoying their family walk so much that she didn't want to return to Kensington Palace.

According to the same report, the little princess tried to walk in the other direction when Kate started to make her way out of the park. This forced the mum-of-three to instruct her 'No, come this way Charlotte', to which she obliged.

Last week, US Weekly revealed that Princess Charlotte already has a great bond with little Louis: 'She is really enjoying having a younger brother to play with. She’s taking her big sister duties very seriously. She won’t leave baby Louis’s side.

‘Charlotte is just like [George]. They have a great bond, and a similar connection is growing between Charlotte and Louis’ – a bond that was evident in the adorable new Prince Louis pictures taken by the Duchess of Cambridge on Princess Charlotte’s third birthday', a source told the publication.

It's not long until we get another glimpse of the royal children again, as both Prince George and Princess Charlotte will be attending Prince Harry and Meghan Markle's wedding on Saturday.