The birth of twins occurs more frequently than one would think, and it's becoming more and more common. Researchers estimate that couples trying for a baby have a 3% chance of conceiving twins, which is a staggering 60% increase on figures recorded in the 1980s. Indeed, many of the celebrities we know and love have a twin brother or sister but most celebrity twins don't share the limelight with their brother or sister.

Take, for example, Scarlett Johansson. Scarlett is three minutes older than her brother Hunter who, despite having a very brief foray into acting, has displayed a keen interest in politics. Hunter has gone on to work alongside US president Barack Obama. Some other celebrity twins have lives that contrast hugely with that of their twin, such as the well-liked actor Ashton Kutcher. His twin, Michael Kutcher, was born at just 4 pounds, while Ashton weighed almost 11 pounds. Michael suffers from cerebral palsy and had to have a heart transplant when he was a child. Michael works as a motivational speaker, and claims that his twin is his best friend.

Yet a select few celebrity twins have managed to achieve fame and fortune together, often in the form of collaboration for TV or film. The following 5 Celebrity Twins are all multi-millionaires, and most of them have been since a very young age. Despite making their money in different industries, these 10 are are all clearly hard-working, determined people. They have undoubtedly worked extremely hard to achieve the lives they live today. Check out our list to find out the combined wealth of the richest twins alive today.

5. Tia and Tamera Mowry - $8 million

Tia and Tamera Mowry were born in the late 70's in Germany, but the pair were raised in Texas. From a young age, Tia and Tamera actively entered talent shows and pageants. They landed their first major role in 1994 as the stars of 'Sister, Sister', a sitcom which ran for five years. This sitcom launched the girls into mainstream success. The girls became heavily involved with the children's broadcasting station Nickelodeon, starring in several of their shows, such as 'All That' and 'Are You Afraid of the Dark?' Tia and Tamera have also worked as voice actresses, Tia for the Bratz films and Tamera for Family Guy.

In recent years, the pair have not stepped out of the limelight. Tia and Tamera starred in three seasons of their own reality TV show, called 'Tia and Tamera', from 2011-2013 which aired on the Style Network (now known as Esquire Network). Season 3's debut pulled in almost 500,000 viewers, meaning that its viewership had increased by 10% since season 2. Despite this, the show was cancelled after the third season. This doesn't mean the twins are not keeping busy, however: Tia has landed a role in the sitcom 'Instant Mom', while Tamera became a talk show host for The Real.

4. Dylan and Cole Sprouse - $16 million

In 1992, Dylan and Cole Sprouse were born in Arezzo, Italy, but they soon moved to California with their parents. Dylan was named after the poet Dylan Thomas, while Cole was named after the singer Nat King Cole. The twins began acting at a very early age, getting small roles in TV shows and commercials. As young children, the two boys often shared roles, taking turns to act in scenes. By the age of seven, the boys had starred in major films and TV series, such as 'That 70's Show' and 1999's 'Big Daddy' alongside Adam Sandler. The boys also branched out into roles separate from one another - Cole played Ross' son Ben on the famous TV series Friends.

However, the two boys really made their money a few years later. In 2005 they were cast in 'The Suite Life of Zack and Cody', a Disney channel show. The show experienced immediate popularity. Dylan and Cole starred alongside other major disney channel stars like Ashley Tisdale and Miley Cyrus. The company Sprouse Bros. was launched due to the success of the show, in order to manage the pair's brand. After years of success, the twins made the dramatic decision to leave the Disney channel, claiming that Disney attempted to steal their idea for a spin-off show. The twins took a break from acting, but they are using their time productively and have been enrolled in New York University since 2011.

3. Ronde and Tiki Barber - $30 million

Ronde and Tiki were born in Blacksburg, Virginia in 1975. The brothers made their fortune when they both became involved with the National Football League, albeit playing for different teams. Ronde spent the entirety of his 16 year career with the Tampa Bay Buccaneers, while Tiki played for the New York Giants. The brothers proved to be competent players. Ronde Barber made over 1000 tackles during his career with the NFL. He is currently a member of NFL's 2000s All-Decade Team. Tiki made history in 2005 when he made a whopping 1800 rushing yards and 500 receiving yards in the course of one season, a first in NFL history.

Tiki shocked fans with an early retirement back in 2007, leaving the New York Giants who went on to win the Superbowl a year later. Tiki attempted to return to the New York Giants in 2011, but the team didn't take him. Ronde retired from playing in 2013. The twins have become involved in various other projects since; they've co-written and published a series of children's books and Ronde states that he will now work as an analyst for Fox Sports 1.

2. Benji and Joel Madden - $32 million

Identical twins Benji and Joel Madden are part of the American punk-rock band Good Charlotte. The twins formed the band in 1996 after attending a Beastie Boys concert. The ambitious twins had never sung or played an instrument prior to this, but they were determined to make it work. For years, the band experienced no success. Benji, Joel and the other members worked minimum wage jobs for years, performing in bars and clubs at night. Epic Records eventually signed the band in 2000.

Benji and Joel are certainly a talented pair. Along with teaching themselves how to sing and play music, the twins also write all of the band's lyrics. The band made a huge amount of cash with their second album, 'The Young and the Hopeless', which went multi-platinum in the US. The band's recent releases have not seen as much success, however. 'Cardiology', which was released in 2010, was panned by critics and failed to sell. The pair seem to have left their punk-rock heyday behind them for now, focusing more on personal relationships and philanthropy - Joel Madden set up The Richie Madden Children's Foundation with wife Nicole Richie.

1. Mary Kate and Ashley Olsen - $300 million

It should be no surprise that Mary Kate and Ashley Olsen take our number one spot. At just 27, the twins have had an extensive career which began when they were 6-month-old babies. The twins began their rise to stardom on the TV show 'Full House', sharing the role of Michelle Tanner. After Full House ended, the Olsen twins quickly moved on to independent projects, creating the brand Dualstar in order to release their movies and TV shows. The girls did extensive work as child actresses, with over 15 films and two TV series under their belts as teenagers. In 2004, they were presented with a star on the Hollywood Walk of Fame.

In recent years, the twins have given up acting to focus on a career as fashion designers. The pair have seen an incredible amount of success- they now design three major fashion labels. Olsenboye is a children's range sold in department stores, while Elizabeth & James and The Row are high-end fashion lines. Their fashion lines are managed within Dualstar, a company of which the twins became sole owners in 2004. The Olsen's Dualstar empire has annual retail sales of over $1 billion. Their career as fashion designers has been going so well that, understandably, the twins have stated that they do not have any current plans to return to their acting career.