An American man who was 14 when his father took him to Syria to join the "Islamic State of Iraq and Syria" (ISIS) was charged with aiding a terrorist group, US authorities announced Wednesday (September 30th).

Jihad Ali, now 19, and his father Emraan Ali were repatriated to the US from Syria, where they were held since last year by the Syrian Democratic Forces (SDF), among hundreds of foreign fighters captured after the defeat of ISIS.

Both father and son were charged in Miami federal court with providing material support to a designated foreign terrorist organisation.

The father, a Trinidad & Tobago-born naturalised American, took his wife, New York-born Jihad, and five other children to Syria in 2015 to enlist in the extremist group.

The father had been inspired by the teachings of US-born al-Qaeda preacher Anwar al-Awlaki.

Jihad Ali told FBI investigators last year that he was "excited to go somewhere new and see the world", according to court filings.

Later in 2015 he entered ISIS weapons and warfare training and was assigned to an ISIS battalion for English speakers, posting boasts of his joining the fighting on Facebook.

"Jihad described some of the training as cool and other portions as scary," the court filing said.

He and his father, now 53, were involved in several combat situations, and were joined by yet another of Emraan's sons, who was not identified by the US Justice Department and was younger than Jihad.

The three surrendered in al-Baghouz in March, the last stronghold of ISIS in Syria, and taken custody of by the SDF.

Jihad and his father both appeared in federal court in Florida Wednesday, the Justice Department said.

There was no indication whether Jihad will be treated differently due to his having been a child when introduced to ISIS.

The charges carry up to 20 years in prison.