Miranda Kerr says her son Flynn loves Katy Perry

Speaking to PEOPLE, she said: "They're great. They get along really well

"We're a modern family. Orlando and I are literally like family, he's like a brother to me. It's very weird, but we really care for each other and we have a great relationship, so I feel very lucky."

Orlando, 40, and Katy, 32, have been dating for over a year, while Miranda, 33, is engaged to Snapchat founder Evan Spiegel.

Meanwhile, earlier this month Katy threw a surprise party to celebrate Orlando's 40th birthday.

The 'Firework' hitmaker delighted her boyfriend with a star-studded bash in Palm Springs, where they were joined by a host of pals, including Amanda De Cadenet, Jennifer Aniston and her husband Justin Theroux.

But the highlight of the evening for the British actor was a surprise appearance from his mother.

He shared a photograph of them embracing on Instagram and wrote: "Best gift ever surprise visit from me mum.(sic)"

Pictures shared on social media showed a number of the guests, including the 'Lord of the Rings' star and his mother, had donned onesies printed with Orlando's face for the celebration, but at one point, the actor and a number of his pals - including Justin - stripped down to the waist and posed for shirtless pictures.

It was previously claimed the singer had also hired a celebrity concierge service to plan 12 months' worth of events to celebrate Orlando's birthday.

A source said recently: "Katy is determined to make this year the best ever and is not letting money get in the way. She wants a combination of holidays and 'bucket list' experiences, including seeing some of the world's most famous sights."