The crimes they are suspected of must have been committed in Stockholm, among other places, during the same period, between March 2011 and September 2021.
The suspected brothers are residents of Uppsala and have been in custody since last autumn.
The big brother, a man in his 40s, was arrested in September on suspicion of espionage.
He was at the time a high-ranking chief within a state authority and already had a background in, among others, the Security Police, Säpo, and the Swedish Armed Forces' intelligence service Must.
Two months later, the man's younger brother, who is also said to have worked at Säpo for some time, was also arrested on suspicion of espionage.
During the arrest hearing, the prosecutor announced that he wants an extended prosecution period until 11 February.
Something that the man's defender Björn Sandin disputed.
- I want my client to be released immediately after the arrest negotiations, Sandin says to Dagens Nyheter.
He is now being remanded in custody for the second time in Stockholm District Court.
On Monday, the remand for the older brother takes place.