Romeo Beckham
Romeo Beckham completed the children's London Marathon in 18 minutes Jason Merritt/Getty Images

Victoria and David Beckham's son Romeo Beckham was in tears as he completed the children's London Marathon in front of thousands of spectators.

The 12-year-old was supported by his "proud" parents and brothers Brooklyn, 16, and Cruz, 10, as he crossed the finish line at the junior race in just 18 minutes and 54 seconds.

As the youngster's family – minus his three-year-old sister Harper – rallied around him, Romeo was seen getting emotional and looked tearful after running the three miles.

With his race completed, Romeo has incredibly raised £6,000 ($9,085) for charities UNAIDS and 7 Fund.

His fashion designer mother Victoria praised her second son on his achievement, writing on Instagram:

Well done Romeo!! We r all so proud!! Running @londonmarathon for UNAIDS and 7 Fund x vb

A photo posted by Victoria Beckham (@victoriabeckham) on

The 41-year-old also shared an Instagram photo of the supportive banners the family brought with them, which included: "Go Romeo" and "Keep Running Romeo." The family gave the youngster plenty of encouragement by wearing T-shirts with "Team Romeo" printed on the front.

His older brother Brooklyn also cheered the young Burberry model on, posting on Instagram:

The children's race is set for youngsters aged between 11 and 17 and is situated from Old Billingsgate to The Mall.

Former footballer Beckham launched the 7 Fund charity alongside Unicef in February which aims to help children at risk of violence, abuse or disease.

The 39-year-old said at a press conference at the time: "Going on the ground to certain places for myself I've always said that part is the really important part of this. Being there, being able to really kind of get into a situation where you can really help in many different ways.

"Whether it's putting a smile on a child's face or helping in other ways giving a bit of positivity, those are the things that I've enjoyed over the last 10 years."