The Duchess of Cambridge's relationship with her sister-in-law Duchess Meghan is ''strengthening''.

It has been heavily speculated since the former 'Suits' star joined the royal family that she and Catherine - who was known as Kate Middleton until she married Prince William in 2011 - weren't as close as fans predicted them to be, but it's believed a friendship is starting to form now that Meghan has two-month-old son Archie with her husband Prince Harry as they have more in ''common.''

longtime royals author Robert Lacey told PEOPLE magazine: ''You're seeing more confidence from Meghan recently but also from Kate.

''She [Meghan] pretty much arrived in the UK and went straight into learning how to be a royal. Moving to a new country is not an easy thing. Then you multiply that it's the royal family and comes with thousands of years of pomp and circumstance. Here she was planning her wedding, which anyone who has done it knows how stressful that is, while also immersing herself in a new country, a new family, a new life, all while living in a fishbowl.

''Coming from different backgrounds, I think, they have more the makings of a team than people imagined. And they have a common interest as partners to these two men who are so crucial to the monarchy, along with their children.''

An insider added: ''They're each a little more relaxed. They have more in common now.''

The royal family all came together at the beginning of the month when Meghan, 37, and Harry, 34, christened their son in a private ceremony at Windsor Castle - where they got married in 2018.

The youngster was baptised wearing a handmade replica of the royal christening gown, with the original being used as early as 1841.

The news was shared with fans via their official Instagram account in a statement which read: ''The Duke and Duchess of Sussex's son, Archie Harrison Mountbatten-Windsor was christened in the Private Chapel at Windsor Castle at an intimate service officiated by the Archbishop of Canterbury, Justin Welby. The Duke and Duchess of Sussex are so happy to share the joy of this day with members of the public who have been incredibly supportive since the birth of their son. They thank you for your kindness in welcoming their first born and celebrating this special moment. Their Royal Highnesses feel fortunate to have enjoyed this day with family and the godparents of Archie.''

Meanwhile, Duchess Catherine, 37, has Prince George, five, Princess Charlotte, four, and 14-month-old Prince Louis with her husband Prince William, 37.