Larry Page, Google's billionaire co-founder, is set to marry his girlfriend, Lucy Southworth, on a tiny Caribbean island this weekend, a source familiar with the wedding arrangements said.

The impending nuptials will create an instant billionaire out of Southworth, who will share in Page's estimated $21 billion fortune.

The couple will hold the ceremony on an island enclave owned by Richard Branson, the billionaire owner of Virgin Group, who will act as best man to Larry, the source said.