There were rumours that the couple were engaged back in September but were keeping it under wraps because they didn't want to take the shine off the birth of Pippa's nephew, and future king, Prince George. There was also talk that a formal announcement would be made at Pippa's 30th birthday on September 6.
Read more: Is Pippa Middleton secretly engaged?
Pippa and her beau made plans to celebrate in private, a source told Us. They would be spending Boxing Day at her family's Buckleberry estate before heading to the Alps for a holiday in the new year, they said.
Read more: Grand plans for Prince George's first Christmas
However, the UK's Daily Mail, has denied the report, saying when the couple arrived home at Heathrow Airport recently there was no sign of a ring on Pippa's finger.
Pippa and Nico were first pictured together in February while on holiday in Mustique with the Duke and Duchess of Cambridge and the Middleton family.
In September, the couple went on another romantic break to the Caribbean, and also jetted off for a shooting weekend in October.
Former Edinburgh University student Pippa and Nico were seen laughing and giggling at the check-in desk before taking a low-cost flight from Inverness to London on their way back from a shoot in the Highlands.
Nico grew up in a red-brick terraced house in a middle-class family in Folkestone before making his millions as a stockbroker at Deutsche Bank.
Pippa has previously dated investment banker James Matthews, 37, and financier and former England cricketer Alex Loudon, 32.
- www.nzherald.co.nz, Daily Mail