If they're good enough for Prince George, Princess Charlotte, and Prince Louis, then they're good enough for the royal children's baby cousin, Inigo!
In this week's issue of HELLO!, James Middleton reveals how his older sister the Princess of Wales has lent some of her children's old baby clothes for her nephew Inigo.
It seems the near one-year-old has an outfit for every occasion, thanks to the hand-me-downs from Kate and their other sister Pippa, who also shares three children with her husband James Matthews and who has been loaning some of their items too.
"They are milestones, because [my sisters] remember when their child was wearing something, and how old they were – it takes them back," James told HELLO!. "It's been a lovely thing for them."
Baby Inigo's royal cousins
Apart from the hand-me-downs, James, who shares his son Inigo with wife Alizée, is also grateful that his baby boy is growing up as part of a tribe who will look out for him.
"He's fortunate to have older cousins who can now pick him up and show him things, and as he grows up, they'll be able to look out for him. There's definitely an element of curiosity [about] a baby that they have."
Full of praise for his two sisters, the 37-year-old author added: "It's been wonderful, seeing them become mothers and being so dedicated and strong. I'm in awe of that."
"I've been fortunate to see how my sisters have done it, and take tips along the way – some I take on board, and others I'm like: 'Hmm,'" he quipped.
His new book
As well as preparing to celebrate his son's first birthday next month, James is also marking another big milestone – the release of his new book, Meet Ella: The Dog who Saved my Life, next week.
It's a tender tale of James's relationship with the cocker spaniel who came into his life when he was 20 and the adventures they encountered along the way, including trips to the Scottish mountainsides, royal weddings and meeting Alizée, the woman who has become his wife.
But it is also a heartfelt story of survival as the Princess' brother, suffering from clinical depression and feeling suicidal, was held back from the brink of despair by his loyal companion.
His idea for the book developed after his wife Alizée discovered she was pregnant with Inigo.
The news came just weeks after their dog Ella died aged 15 and, mourning her loss, James wanted a way to share his memories with his son.
To read the full exclusive interview, pick up the latest issue of HELLO! on sale in the UK on Monday. You can subscribe to HELLO! to get the magazine delivered free to your door every week or purchase the digital edition online via our Apple or Google apps.
Meet Ella by James Middleton is published by Radar on 26th September. In celebration of his dog Ella, James Middleton is supporting Dogs Trust and its very first 'Walk for Our Old Friends' (WOOF) event in October which encourages people to walk in memory of their beloved canine companion. Find out more at https://events.dogstrust.org.uk/woofevent
Photos by Richard Murgatroyd Photography