Kate Middleton and Prince William may be reunited with some long lost relatives during their trip to Australia.

Two suburban families have discovered they have a familial connection with the Duke and Duchess of Cambridge.

It has been revealed that mine worker Mark Lowers, 46 from the bayside area of Birkdale in Brisbane is Kate's second cousin.

He said that he discovered the royal connection after investigating his family tree in 2008.

"I found out that my mum Lillian, and Kate's mum Carole, had the same grandmother, Edith Eliza Chandler," he explained.

"That makes them first cousins and makes Kate and me second. I guess the little fella George is a third cousin of some sort," he added.

"Carole and Mum wrote Christmas cards to each other for years then lost touch."

Lowers said he'd like to invite the royal family to his home for a barbecue.

"I'd love to have them over, throw a few snags [sausages] on the barbie and crack a few cold ones but I don't think they're going to have time!"

Meanwhile, 74-year-old Neil Geary revealed that he is Prince William's 14th cousin.

His wife Barbara traced his lineage back to 1749 and found that he and William both descend from the children of William Conyngsby and Beatrix Thursby.

"Trust me, no one is more shocked than I am," said Geary. "I wrote to the Palace back in 2009 and was chuffed when we got the letter saying that William was very pleased to hear about his Australian relations. I'm very proud to know that William and Harry are family."

Geary has asked the Governor of Queensland for an invitation to a VIP Royal luncheon planned for April 19, so that he might have an opportunity to meet his royal relations.

"So far no invitation has arrived but I understand the pressure of having to invite all the rellies," he said.

The Duke and Duchess of Cambridge will arrive in Australia on April 16 for the 18 day trip, which marks the couple's first official tour of the region with Prince George.