Ever since the summer of 2006, when Fidel Castro was taken ill and transferred power to his brother, there has been speculation about the amount of power he wields behind the scenes.
Some say that his brother, the diminutive Raul, defers to him. Others say that Raul is in charge, but is hampered in his desire to transform the country by a fear of offending his elder brother.
The truth is we simply do not know. All we can say for sure is that the Castro brothers are still in charge.
The true nature of the bond between the two men is still a mystery. They keep their private lives to themselves, and their relationship is tightly kept under wraps.
The brothers have been inseparable since they went to boarding school together and they remain so now, at least in public.
What has changed is that now the younger, less loquacious and somewhat more camera-shy Raul is running the country, and has slowly replaced his brother's allies in government with his own.
He is also pursuing an economic policy that one would not have associated with Fidel.
This month's Communist Party Congress, the first in 14 years, is set to approve a raft of proposals that will transform the way the economy runs. It is also set to vote to change the official definition of socialism from the pursuit of egalitarianism - equal outcomes - to one of equality of opportunity.
Some commentators say the changes highlight the differences between the two brothers.
However, such speculation ignores the fact that Fidel, too, has been pragmatic in the past when necessity has driven the agenda - in the early 1990s, after the withdrawal of support from a collapsing Soviet Union, Fidel introduced a raft of measures to liberalise the economy, including legalising the US dollar.
There is no reason to assume that he is not in favour of the current changes.
From the earliest days, the Castros have tried to build a consensus before embarking on major changes.
Under Fidel, that consensus was often arrived at by unconventional methods - he would call a meeting in Revolution Square, two million people would show up and he would ask for a show of hands.
With Raul in charge, policy decisions are made in meetings. He is a manager, not a leader.
So what does the former leader do now? He spends his time writing, mainly on foreign affairs, and publishing a regular column that appears in the Communist Party daily newspaper Granma.
His "reflections", as they are called, are of variable quality and sometimes quite cryptic, giving the impression that he is not altogether in charge of his faculties all of the time.
Yet the reflections do make for an interesting read.
It appears that Fidel is prone to conspiracy theories and avidly reads more esoteric web offerings on such matters as the BP oil disaster and the nuclear problems in Japan.
He also has a knack of getting it right - recently, he was among the first to predict that Nato would intervene in Libya, long before it became apparent that France and Britain could get a resolution through the UN.
Rank and file delegate
On the whole, Fidel keeps out of domestic affairs, and when he has publicly intervened it has been in support of his brother - such as when he published an outspoken criticism of his former favourites Felipe Perez Roque and Carlos Lage, who were removed from office in 2009 after having been seduced by "the honey of power", Fidel said in an online article.
The men are also rumoured to have been caught making off-colour jokes about Raul.
Fidel's timely quip to a US journalist last year that the Cuban model "does not even work for us anymore" (later denied) had the effect of legitimising his brother's economic plans.
The Party Congress was announced in the week following the hullabaloo which surrounded that remark.
More recently, Fidel caused another stir with an apparently off-the-cuff admission when he said he had ceased to be general secretary of the Communist Party five years ago - something that had not been announced earlier.
Had he forgotten? The matter is one of constitutional importance - if he wasn't general secretary, then who was?
Of course, his brother has been running things as he is the "second general secretary", and presumably the Congress will shortly ratify his promotion to general secretary. (Fidel, incidentally, will be present as a rank-and-file delegate.)
That Fidel can do this without so much as raising an eyebrow is indicative of his enduring role at least as a figurehead.
As the architect of a socialist revolution that has survived for 50 years just 144km (90 miles) from the United States, Fidel Castro attracts plenty of respect, if not admiration.
Many Cubans on the island are proud, whether or not they agree with all his politics.