Aisha Gaddafi, the daughter of late and deposed Libyan leader Muammar Gaddafi has contacted the International Criminal Court, in the Hague, concerned about the fate of her captured brother, Saif al-Islam Gaddafi.
Saif al-Islam Gaddafi was captured by the new Libyan authorities in November in the city of Zintan.
He is currently detained awaiting trial on rape and murder charges. If convicted he could face the death sentence.
Gaddafi's son was also facing an arrest warrant from the International Criminal Court for alleged crimes against humanity following his role in the civil war to deposes his father. If convicted by The Hague's court he faces a jail sentence but Libyan authorities insist he should be tried in Libya.
His supporters fear he will not receive a fair trial in Libya.
His sister Aisha has now submitted a document to the ICC, asking the court to take into account "concrete information" she believes "will assist the pretrial chamber in determining the appropriate course of action it should take " CNN reported.
The document suggests that the Libyan authorities refuse to let a foreign lawyer act for Sail al-Islam and states that Aisha "wishes to protect the interests of her brother ... whose exact whereabouts are presently unknown to her and whose fate is currently the subject of confidential litigation."
The appeal also asked for a court appointed experts to examine Saif al-Islam's mental and physical state and called on the Libyan authorities to say whether and when they intend to hand him over to the court.