Ummariyat Mirza, 21, of St Agathas Road, Birmingham, is charged with preparing for a terrorist attack in the UK by buying a knife and other items.
His sister, Zainub Mirza, 23, from Eastfield Road, Bordesley Green, is charged with sending Islamic State propaganda videos to others.
They were remanded in custody at Westminster Magistrates' Court.
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The siblings were ordered to appear on 28 April at the Old Bailey for a preliminary hearing.
It is alleged Ms Mirza sent the extremist material, including a picture of a man holding two severed heads, to encourage terror attacks.
Mr Mirza was arrested by counter-terror police in Alum Rock Road, Birmingham, as part of a series of raids on homes on 29 March.
He is also charged with possessing the bomb-making guide the Anarchist Cookbook and an extremist document called the Mujahideen Poisons handbook.

Steven Tolley, 48, from Tiverton was one of three men injured while working on the northbound carriageway of the A361 at Gornhay Cross, Tiverton.
He was airlifted to Derriford Hospital after the collision on 29 January but died on Monday.
The driver, 43, from Saltash, was arrested on suspicion of dangerous driving and bailed until 20 May.
Another worker in his 40s was airlifted to hospital for treatment for "serious injuries" and a third was described as "walking wounded". Both are now recovering at home.
All three were employed by the South West Highways team which said it had informed its staff of the "sad loss" and was in touch with Mr Tolley's family.
It added that there would be an internal investigation into the incident "as a matter of course".
The police and the Health and Safety Executive are also investigating the incident.
Anyone with information is urged to contact the police.
A man accused of plotting a terror knife attack has appeared in court alongside his sister.
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A road worker who was critically injured in a collision involving a van in mid Devon has died.