Two months ago, the older brother, who is in his 40s, was arrested on suspicion of espionage.
At the time of his arrest, he was a senior official in a government agency.
He had previously been employed by the Security Police and by the Swedish Armed Forces' intelligence service Must.
Last week, the younger brother, who is in his 30s, was also arrested.
Both brothers deny the crime but were arrested last Friday on probable cause on suspicion of aggravated espionage.
According to information to SVT, the younger brother must also have worked at Säpo for some time.
The information is confirmed by several independent sources within the Security Police.
It is unclear whether the brothers worked there at the same time and what their duties consisted of.
Studied to be a police officer
The prosecutor believes that the brothers have seized foreign power and been guilty of gross espionage.
The crimes are suspected to have been committed between March 2011 and September 2021.
During the same period that espionage is suspected to have begun, in 2011, the younger brother studied the first semester of the police program.
It shows documents that SVT has received from the Police Authority.
However, he did not complete police training and was denied study grants in the spring semester of 2012.
Links to Iran
The older brother worked during this time at the Swedish Armed Forces' intelligence and security service Must.
According to information to DN, he then served at Sweden's most secret intelligence agency - the Office for Special Collection, KSI - where one of the assignments is to recruit sources and defectors from other countries' intelligence services.
The suspects were born in Iran but grew up in Uppsala, where they are still registered.
It is currently unclear whether the suspicions have links to Iran.
The prosecutor in the case does not want to comment on the new information.
SVT has also sought the younger brother's defender who has not been reached for comment.
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