So how DID they keep it secret? Anna Kournikova and Enrique Iglesias 'went undercover' for her entire pregnancy before welcoming baby twins

Enrique Iglesias and Anna Kournikova welcomed twins, Nicholas and Lucy, over the weekend in Miami.

And Anna, 36, and Enrique, 42, managed to keep her pregnancy a secret by staying 'undercover,' according to People.

The magazine's source said that: 'A friend told me like five months ago [that] they were pregnant but keeping it very, very undercover.'

Undercover agents: Anna Kournikova and Enrique Iglesias kept the former tennis player's pregnancy a secret for nine months by going 'undercover' (pictured July 2016)

Undercover agents: Anna Kournikova and Enrique Iglesias kept the former tennis player's pregnancy a secret for nine months by going 'undercover' (pictured July 2016)

People's insider, who said they did everything to keep it 'completely secret,' added that: 'I saw her cute belly.'

They also revealed that Anna and Enrique usually just spent time with their family and close friends, noting that they 'mostly keep to themselves.'

People wrote that while they are private individuals, they are also 'very generous to local charities.'

They welcomed their son, Nicholas, and their daughter, Lucy, in Miami on Saturday, according to TMZ

Proud parents: The sportswoman, 36, and the singer, 42, welcomed daughter Lucy and son Nicholas in Miami, Florida, over the weekend (pictured in November 2011) 

Proud parents: The sportswoman, 36, and the singer, 42, welcomed daughter Lucy and son Nicholas in Miami, Florida, over the weekend (pictured in November 2011) 

The former professional tennis player and the Hero singer kept the pregnancy a secret.

On Saturday, Kournikova posted three photos on Instagram, featuring herself on a boat with the tag 'no filter needed'. Her figure was swamped by an Iglesias jacket from his recent tour. 

The new parents have been dating since 2001 after meeting on the set of the Spanish singer's Escape music video, but are not thought to be married. 

Surprise! The long-term couple surprised fans when their baby news was revealed on Monday (pictured in September) 2010

Surprise! The long-term couple surprised fans when their baby news was revealed on Monday (pictured in September) 2010

Mom's the word? On Saturday, Anna posted three photos on Instagram, featuring herself on a boat with the tag 'no filter needed'. Her figure was swamped by an Iglesias tour jacket

Mom's the word? On Saturday, Anna posted three photos on Instagram, featuring herself on a boat with the tag 'no filter needed'. Her figure was swamped by an Iglesias tour jacket

Anna and Enrique are notoriously secretive about their relationship and haven't been seen together in public for nearly a year.

Last year Anna sparked marriage speculation when she began sporting a large diamond ring and matching eternity band on her wedding finger.

However in an interview this summer Enrique revealed that despite the length of time they've been together, he and Moscow-born beauty Anna have no immediate plans to get married.

The last picture: The two have been out of the spotlight since they were seen in a selfie last year with Anna's little brother Allan

The last picture: The two have been out of the spotlight since they were seen in a selfie last year with Anna's little brother Allan

Enrique claimed they already live the life of a married couple in many ways. 

Enrique once raised eyebrows when he introduced Anna as his wife during a concert in Russia in 2011.

But the musician claimed he simply got caught up in the moment, adding that being married or not has no bearing on how much he loves his long-time partner. 

It's love! The two met on the 2001 set of Enrique's music video for Escape

It's love! The two met on the 2001 set of Enrique's music video for Escape

Future parents: The couple have been dating since they made the video 16 years ago

Future parents: The couple have been dating since they made the video 16 years ago

Reflecting on the incident, he previously shared: 'It was just meant to be sweet, in the moment. I honestly didn't mean to confuse people. I thought it'd be easier for the audience to understand than if I said, "my girl".'

And the son of singer Julio Iglesias added: 'I've never really thought marriage would make a difference. 

'Maybe it's because I come from divorced parents, but I don't think you love someone more because of a piece of paper. 

Happy parents: Enrique Iglesias and Anna Kournikova welcomed twins, Nicholas and Lucy, over the weekend in Miami; seen in 2002

Happy parents: Enrique Iglesias and Anna Kournikova welcomed twins, Nicholas and Lucy, over the weekend in Miami; seen in 2002

'And nowadays it's not taboo to have kids and not be married. What makes a difference is that you're a good parent.'

Anna also told Women's Health in 2011 that marriage 'isn't important' to her - only if she's in a happy relationship.

The blonde beauty said to the magazine that she 'believes in commitment,' being 'open' and 'trusting and respecting each other completely.' 

Anna told Women's Health she wants children, 'whether I have my own or adopt. I love taking care of people.' 

Happily ever after: Anna also told Women's Health in 2011 that marriage 'isn't important' to her - only if she's in a happy relationship; seen in Sunrise, Florida in 2012 for Jingle Ball

Happily ever after: Anna also told Women's Health in 2011 that marriage 'isn't important' to her - only if she's in a happy relationship; seen in Sunrise, Florida in 2012 for Jingle Ball

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