OLD AND RICH

1. Maria Franca Fissolo, 99

A lifetime spent in close contact with sweets has not prevented Italian Fissolo, worth US$25.2 billion (S$35.2 billion), from living to a ripe old age.

Her father-in-law Pietro Ferrero created the spread now known as Nutella and founded the Ferrero Group, the company behind Ferrero Rocher and Kinder chocolates.

Fissolo married her late husband Michele in 1962, with whom she had two sons - Giovanni and Pietro. Giovanni is the current head of the Ferrero Group.

2. Henry Hillman, 98

Worth an estimated US$2.6 billion according to Forbes magazine, the American has devoted much of his twilight years to the charity foundation bearing his name.

Hillman made his money in real estate, private equity and venture capital.

Fun fact: He was born on Christmas Day, 1918.

3. Teo Woon Tiong, 98

Local shipping magnate Teo, who is also known as YC Chang, founded Pacific International Lines (PIL) in 1967.

Mr Teo sailed cargo on Chinese junks between Malacca and Indonesia before starting his company, and once lost his fortune to a pirate attack.

He is now worth an estimated US$1.7 billion.

4. Anne Cox Chambers, 97

Only 227 of the 2043 people who made Forbes' 2017 billionaire list are women, but Anne Cox Chambers joins Maria Fissolo as the second woman on the oldest billionaires list, proving again the well-established fact: women enjoy a higher life expectancy than men, even among billionaires who can afford the very best of healthcare.

Chambers, worth some US$17 billion, is the surviving daughter of Cox Enterprises founder James Cox. Now a massive conglomerate, Cox Enterprises has interests in the automobile and media industries.

5. Aloysio de Andrade Faria, 96

Faria, worth US$2.4 billion, is a Brazilian banker who transformed his family's bank into one of the largest in Brazil. While his conglomerate Banco Alfa today runs the gamut from finance to palm oil production to hotels, Faria was actually trained as a paediatrician in his youth.

He is also known to be an extremely private individual.

EARLY BLOOMERS

1. Alexandra Andresen, 20 and Katharina Andresen, 21

The Andresen sisters are clear outliers in a group that overwhelmingly features individuals who are male and over 60 years old.

Among women billionaires under the age of 40 however, Alexandra and Katharina are fairly typical in having inherited their money (both are worth US$1.2 billion each). According to Forbes, only one of 14 women billionaires aged 40 or younger made her own fortune: Chinese gas distribution billionaire Zhou Yifeng.

2. Gustav Magnar Witzoe, 23

Gustav Magnar owns 47 per cent of Norwegian salmon giant Salmar ASA's equity, a gift to him from his father (also called Gustav) in 2013.

The younger Witzoe is worth US$1.5 billion, but isn't content to just take over the family business from his father - he's also trying to make his own mark in real estate and as a tech start-up investor, according to Forbes.

3. John Collison, 26

Irishman Collison (worth US$1.1 billion) is the world's youngest self-made billionaire. Co-founder of online payment processing company Stripe along with his brother Patrick, the pair hatched the idea for the company while John was still an undergraduate studying physics at Harvard.

4. Evan Spiegel, 26

Unlike Mark Zuckerberg and Facebook, Spiegel is considerably less well-known than the social media platform he created: Snapchat.

But that's perfectly fine, because Spiegel is now worth $4.5 billion, and also became the youngest public company CEO when Snap Inc began trading earlier this month.

5. Ludwig Theodor Braun, 27

Ludwig (worth US$1.1 billion) is the youngest scion of the family that gives its name to and runs medical and pharmaceutical device giant B. Braun Melsungen AG.

Most people will know of the German company, family-run since it was founded in 1839, from its Oral-B line of electric toothbrushes.