Layth, 14, was found murdered in Upplands-Bro after a kidnapping.
Two young men and a woman are now in custody.
But the killer is still being hunted.
A total of six people are suspected in the case after the murders of the two 14-year-olds from Nyköping.
According to district court documents, the first victim must have been kidnapped at an address south of Stockholm between July 24 and 25. He was then murdered sometime from July 25 until the evening of July 29, when he was found dead in a forest area in Nynäshamn municipality.
A 17-year-old boy and a 21-year-old man have been in custody since last week on suspicion of aiding and abetting murder and kidnapping.
The second victim, 14-year-old Layth, was found murdered in an outdoor area in Upplands-Bro on 18 August. A 15-year-old boy, who had applied for police protection, has been in custody for almost a month and is suspected of aiding and abetting murder.
Address in Järfälla current
Today, the Södertörn district court remanded two more people, aged 18 and 19, for aiding and abetting the murder of Layth between 27 July and 18 August. Both men are also suspected of kidnapping at an address in Järfälla on 27 July. The 18-year-old is also being investigated for drug offences.
In addition, a 21-year-old woman was detained for attempted gross protection of a criminal, which is believed to have been going on at a residential address in Järfälla until the day the arrests took place earlier this week. Both the woman and the 18-year-old man are listed at the address.
No one has yet been charged with murder. The prosecutor has stated that more arrests may take place.
According to information, the criminal suspects are linked to the “Kurdish Fox”.