The four were seen as crucial members of a pro-Syria establishment that controlled Lebanon at the time of the killing.
A report from Detlev Mehlis, the former chief UN investigator into the al-Harriri assassination, alleged that Mahmoud Abdel Aal had called Emile Lahoud, the former Lebanese president, on his mobile minutes before the huge explosion that killed al-Harriri and 22 others. Lahoud denies the call was ever made.
The Abdel Aal brothers are part of a pro-Syrian, Sunni group called the Ahbash.
The registrar of the tribunal said on Tuesday he expected the prosecutor to ask for detainees to be transferred to The Hague.
Daniel Bellemare, the case prosecutor, has 60 days from taking office to request the transfer of people and evidence.
He has yet to name suspects in the assassination, which anti-Syrian Lebanese politicians have accused Damascus of orchestrating.
Syria has always denied any involvement in the killing, which was followed by a string of further assassinations targeting figures opposed to Syrian influence in Lebanon.
Jarjoura had been charged with giving a false statement, while the other two had been accused of direct involvement in the February 14, 2005 killing that triggered international pressure on Syria to withdraw troops from Lebanon.
The judge set a bail of $330 each for Mahmoud Abdel Aal and Ahmed Abdel Aal, brothers who were detained in October, 2005.
Bail was set at $66 for Jarjoura, who was detained in January, 2006.