Pippa Middleton is reportedly secretly engaged to her boyfriend Nico Jackson.

Britain's Duchess of Cambridge's sister, 29, will wed the stockbroker, 35, next spring and is excited for the upcoming nuptials.

One friend told the Sunday People newspaper: ''Pippa loved seeing Kate go down the aisle and now it is her turn for a fairytale wedding.

''She couldn't be more sure that Nico is the right man for her. They are such a good fit for each other and their families get on really well. Everyone is so happy for Pippa.''

Nico is believed to have proposed to her just before the Wimbledon tennis tournament in June this year and a formal announcement for the engagement is expected after the brunette beauty's 30th birthday on Friday (06.09.13).

The pair were delaying the announcement until Pippa's sister safely delivered her first baby with Prince William.

The source explained: ''They didn't want an announcement before Pippa's birthday because they didn't want to take the shine off Kate and her baby.''

Nico and Pippa - who have been dating for more than six months - are on a romantic Caribbean holiday in secret and they are thought to be renting a villa on one of the tropical islands.