Salman bin Abdulaziz will ascend to the throne of Saudi Arabia after a single year as its crown prince.
But his ailing health, conservative outlook and controversies over funding terrorist groups put him at odds with his moderate predecessor, King Abdullah.
Over the last year, the 79-year-old had increasingly taken on the duties of the former ruler as his half-brother's own health deteriorated.
With reports that King Salman is battling with both Alzheimer's and dementia, his former task as ruler-by-proxy could be taken by another member of the sprawling royal family. He has suffered at least one stroke which left him with limited movement in his left arm.
His own successor was announced as Prince Muqrin bin Abdul Aziz February 2013, to ensure the royal family's continuity.
The 71-year-old, who was educated at the Royal Air Force College in UK, has been serving as the second Deputy Prime Minister and Director General of the Saudi Intelligence Agency.
It's believed Prince Salman collected funds to support the Mujahideen - of whom Osama Bin Laden was a famous figure - to fight the Soviet Union in Afghanistan in the 1980's.
According to Yossef Bodansky, who wrote 'bin Laden: The Man Who Declared War on America': 'Salman maintained clandestine contacts with bin Laden on behalf of Riyadh to channel Saudi support for Islamist jihads worldwide.'
Between 1998 and 2003, he also headed a committee which funded the Palestinian Mujahideen around £53 million, according to the book Understanding Islamic Charities - edited by John Alterman and Karin Von Hippel.
Pro-Israeli groups went through financial transactions to conclude the Popular Committee for Assisting the Palestinian Mujahideen gave the country an estimated £2.4billion during that time.
It says: 'Although it is likely that only a small fraction of that money went to combatants, Saudi official statements endorsing violence against Israel and pledging support for the families of fighters who died and the lack of any apparent safeguards against money going to fighters suggest some degree of support for armed conflicts against civilian targets.
King Salman has 13 children from his three wives. With his first wife Sultana bint Turki Al Sudairi - who passed away at the age of 71 in July 2011 - he fathered Prince Fahd, Prince Ahmed, Prince Sultan, Prince Abdulaziz, Prince Faisal and Princess Hussa.
Sultana was the daughter of Salman's maternal uncle, a former governor of Asir Province.
His second wife, Sarah bint Faisal Al Subai'ai gave birth to Prince Saud.
And the children from his third marriage to Fahda bint Falah bin Sultan Al Hithalayn were Prince Mohammed, Prince Turki, Prince Khalid, Prince Nayif, Prince Bandar and Prince Rakan.
The King's second son Prince Sultan bin Salman was the first Arab of royal blood - and the first Muslim - to fly into outer space.
He flew aboard the Space Shuttle Discover in June 1985 and has occupied the post of Deputy Minister of Oil since 1995.
King Salman served as Saudi Arabia's Defence Minister from 2011. He was head of the country's military when it joined the US and other Arab countries in carrying out airstrikes in Syria in 2014 against Daesh.
He takes the helm at a difficult time for the 'ultra-conservative' Muslim kingdom. The oil-rich country is in the midst of dealing with the social pressures of a young population, who's progressive views have resulted in criticism of the royal family.
The son of Saudi Arabia's founder King Abdul-Aziz Al Saud - who's thought to have had over 50 sons to multiple wives - he's the latest in a line of ageing sons to become King.
He has extensive contacts among the country's tribes and his influence is further strengthened through a network of family businesses, including a stake in the pan-Arab newspaper, ASharq Al-Awsat.
It's thought he will be a much sterner leader than King Abdullah, who's been cited as an instigator of change in the country, but people said the same of his predecessor, Jane Kinninmont from the Chatham House think tank told MailOnline.
The Deputy Head of the Middle East and North Africa programme said: 'I think Abdullah has been quite careful here. He has designated the ruler and his predecessor, and he's ensured there won't be a much more conservative ruler that will scrap his legacy.'
When he was named Crown Prince in August 2012, US President Barack Obama issued a statement praising Salman as 'a man of deep faith who is committed to improving the lives of the people of Saudi Arabia and to the security of the region'.
He wrote: 'The United States looks forward to continuing our strong relationship with Crown Prince Salman in his new capacity as we deepen the longstanding partnership between the United States and Saudi Arabia.'
Now, Ms Kinnimont believes China could eventually replace the US as the country's 'closest allies'. The far-Eastern country is dependent on the Middle-East for most of its oil - and some politicians inside Saudi Arabia have criticized the Americans for not coming down 'hard enough' on Daesh.
But she claims 'China is not interested in sending troops to the Gulf' and it's only really the US who can provide the security Saudi Arabia needs.
'Whoever is King, doesn't have a lot of options in the short term to move away from the alliance with the West,' she said.
At 79, Salman may have a limited time to establish his own which could pave the way for younger, more progressive rulers.
She added: 'Given that Salman is going to have limited time and capacity to run things, you will see younger princes already having more influence, but there's very difficult challenges the country faces with the violence in Iraq and now a coup next door in Yemen.
'It's going to be a really testing time and they can't afford to get too caught up in family squabbling.'
At a relatively young age, King Salman became the governor of Riyadh in 1963 and oversaw its transformation from an isolated deser town into a modern metropolis - bustling with skyscrapers and Western food chains - over the next 48 years.
He also saw it struggle to keep up with demand for affordable housing and sufficient public transport for its four million residents.
The post made him well known internationally, as he played host for VIPs and international envoys and helped secure foreign investment.
