Meet Elton John and David Furnish's two 'unbelievable' sons Zachary and Elijah

They're one of the most famous and recognisable couples in showbiz, but less is known about Sir Elton John and David Furnish 's private life.

The legendary musician, 77, and his husband, 61, have been together for decades and made things official when they wed in 2014, nine years after their civil partnership ceremony in 2005.

Although Sir Elton has always led a very public-facing life, he has been more private when it comes to their sons.

© Theo Wargo

The couple would share the occasional photograph when the boys were much younger, but since then, Zachary and Elijah aren't often seen out in public with their famous dads, and most photos shared on social media conceal their faces to protect their identity as much as possible.

Elton and David have shared the odd anecdote and story about their boys over the years.

Get to know the couple's two young sons here…

Zachary Jackson Levon Furnish-John, 13

Elton and David welcomed their first son into their family on Christmas Day 2010.

Their eldest was delivered via surrogate and, at the time, the happy news was confirmed in an official statement from the couple: "We are overwhelmed with happiness and joy at this very special moment.

© Dave Benett/Elton John AIDS Foun

"Zachary is healthy and doing really well, and we are very proud and happy parents."

The couple opted for surrogacy in accordance with the Center for Surrogate Parenting in Encino, California.

© Getty Images

According to the MailOnline , the couple reportedly paid the surrogate, whose identity has been kept hidden, a lump sum for giving birth to their firstborn.

Elton and David have chosen to keep the name of their surrogate secret and hidden from the public to protect her identity but it was previously reported that they had a brilliant relationship with her but wanted to keep her protected from the public.

Shortly after becoming a first-time dad, Elton spoke with Canada's eTalk and said that fatherhood was "the best decision we've ever made."

The Oscar and Grammy-winning musician said: "We're pretty happy anyway. We've been together [for] 17 years, our careers are both going brilliantly. But this…everyone said, 'You won't believe what will happen to you.' You can't put into words how much love we have for this little boy."

Not much is known about Zachary's personality as he's grown up, but he was previously pictured watching his dad's beloved football team Watford FC, proving that he's inherited his dad's love of the beautiful game.

Elijah Joseph Daniel-Furnish, 11

On January 11 2013, Elton and David's family expanded when they welcomed their youngest, Elijah.

The couple welcomed Elijah via the same surrogate they had welcomed into their family three years prior to having Zachary.

The singer said at the time in a statement: "Both of us have longed to have children, but the reality that we now have two sons is almost unbelievable."

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The family of four resided in Windsor and Elton's enormous estate close to the royal residence and the boys were educated at the local school. However, the children have spent time Stateside since Elton and David own property in the US.

Shortly after Elijah was born, David told PEOPLE the sweet way they had marked the births of their boys: " We kept a scrapbook for Zachary with all his scans, emails with the surrogate, and key moments from the surrogacy, and we are doing the same for Elijah.

"We want the boys to understand the spirit and love that was at the heart of the process."

MORE: David Furnish shares rare glimpse inside family life with Elton John and kids

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© Getty

As for whether his sons would pursue music like their famous dad, the superstar has said he's not entirely sure, but if so, he would be more than proud.

"Of course, whatever their dreams and ambitions are, my husband David and I will fully support them," he told E! News.

Earlier this year, the family marked Elijah's 11th birthday with a delicious and colourful cake. Writing on Instagram, he said: "Happy Birthday to our beautiful son Elijah. Can't believe you’re 11! You fill our hearts with so much love and laughter. We love you. Papa and Daddy xo."