The expected registration of the president's 36-year-old son, Gibran Rakabuming Raka, as a running mate for the favourite to become the next president has raised worries of a resurgence of patronage politics in a country that emerged from authoritarian rule 25 years ago.

Gibran's bid to become vice president was enabled by a Constitutional Court ruling removing a minimum age requirement of 40 for presidential or vice-presidential candidates, on the condition they have been elected to regional posts. Gibran was elected the mayor of Surakarta city in 2020.

Enny Nurbaningsih, a judge and spokesperson for the Constitutional Court, said it had received seven complaints filed by activists and others, of a suspected "ethical violation" in connection with the ruling last week by a nine-judge bench.

One complainant called for the court's chief judge, Anwar Usman, who is the president's brother-in-law and Gibran's uncle, to step down, she said. She did not elaborate.

"We leave this matter to the council. We will not intervene," she told a late Monday press conference, referring to an ethics council the court has set up to look into the complaints.

Anwar, who also attended the press conference, did not comment on the complaints but said he abided by his judicial oath.

A law professor at the University of Indonesia, Titi Anggraini, said any decision the panel makes would not have any impact on Gibran's bid to get elected as it was investigating the judges for a possible ethical breach, not their ruling clearing the way for him to run.

Jokowi, as the president is popularly known, must step down after serving a maximum two terms. He has brushed off fears of he is building a political dynasty saying the people would decide with their votes.

Gibran has been named as the vice presidential candidate of Defence Minister Prabowo Subianto, who is leading in opinion polls to win the election in February.

The two are expected to register as candidates with the election commission on Wednesday.

(Reporting by Ananda Teresia; editing by Robert Birsel)