While the absolute monarchs King Hussein of Jordan and King Hassan of Morocco left their thrones to their eldest sons, the absolutist commoners ruling in Syria and Iraq are grooming second sons to inherit power.
The Syrian President, Mr Hafez al-Assad (69), put forward Bashar, his second son when Basil, the eldest and presumed heir was killed in a car crash in 1994. Bashar, like King Abdullah II of Jordan, never expected to be drafted into politics.
An ophthalmologist trained in Britain, Bashar (34), is expected to be appointed vice-president so he would be in position to fill the job his father has held for 28 years. While Bashar still does not occupy a government post, he has been systematically prepared to assume office.
He underwent army staff training after which he was raised to the rank of colonel. Since then he has been given command of Republican Guard units as well as responsibility for certain areas of army and airforce intelligence.
For the past five years Bashar has handled the extremely sensitive "Lebanon portfolio", formerly managed by the senior Vice-President, Mr Abdel Halim Khaddam. Last weekend Col Assad consulted with Lebanon's President, Gen Emile Lahoud, on the peace process and other regional developments.
He also meets frequently with the Hizbullah and Amal movements leading the liberation struggle against Israel in the south of the country.
In July Col Assad met with King Abdullah and held talks with King Fahd of Saudi Arabia and Crown Prince Abdullah in Riyadh. He is scheduled to visit to Iran soon.
The Iraqi President, Mr Saddam Hussein (59), has also been discreetly preparing his younger son, Qusay (31), for the succession. The elder, Uday, who survived an assassination attempt several years ago, is highly unstable.
While Uday has for many years played a very public role on the sporting scene and as editor and publisher of the daily Babil, Qusay has worked covertly behind the scenes securing the absolute loyalty of the security services.
Last month Mr Saddam declared that Qusay would take charge at times of emergency although he was not formally designated as his father's heir. This was the first official indication that Qusay was in line for the succession.
Mr Saddam, who celebrated the 20th year of his rule in July, can be expected to solidify Qusay's position in coming months.
For both Mr Assad and Mr Saddam the succession issue is very important because both head minority regimes determined to perpetuate themselves rather than risk bloody retribution from disaffected majority populations.
Mr Assad comes from the very small schismatic Alawite community based in the mountains on the north Syrian coast. His rule, based on a clique of Alawite, Christian and Druze officers at the apex of the Syrian armed forces, has given rise to considerable resentment in the majority Sunni Muslim community. The Baath Party has not been used effectively to generate widespread support.
Mr Saddam came to power through the Iraqi wing of the Baath Party. He relies on elite Praetorian and Republic Guard units in the army as well as four highly efficient security agencies, commanded by Qusay, to keep him in power. The Iraqi regime consists for the most part of orthodox Sunni Muslims, the community which forms the majority at the centre of the country around the capital. But more than 60 per cent of the populace is heterodox Shia who have, traditionally but not meekly, accepted Sunni rule.
Furthermore, Mr Saddam's immediate entourage is made up of loyal members of his own clan which comes from the area of Takrit north of Baghdad. This means the regime, a clique within a minority, has a very narrow popular base. The Baath Party tried to compensate for this by organising the populace. But party structures have broken down over the past nine years due to the gradual economic collapse of the country under the punitive UN sanctions regime.
While the ailing Syrian president began grooming Bashar as soon as the elder son died, Mr Saddam, who is in good health, seems to have moved Qusay into position as a result of the recent deaths of the Jordanian and Moroccan monarchs. Clearly, with commoners as with kings, uneasy lies the head that wears the crown, checked Arab headdress or army cap.