Law enforcement in Brussels carried out a wave of raids on Friday and Saturday, charging Mohamed Abrini and a man identified only as "Osama K." by authorities with aiding last month's Brussels suicide bombers.
Swedish media say Osama K. is Osama Krayem, and in an interview with TV4 Sweden a woman said to be his aunt claimed the family was unaware of his involvement in the bombings, but he had "disappeared".
"Suddenly he had just disappeared," Akhlass Daabas, told TV4. "Nobody in the family knew about this. Then he called from abroad and said, 'I'm with them, I'm not coming back.'"
She said the family had failed to keep in touch with him.
"A few months ago his mother went to see him in Turkey, but it didn't work out. She couldn't do that. After that he moved or travelled, so they never met up," she said.
Swedish media quoted Krayem's family as stating he was radicalized in a "basement mosque" in his hometown of Malmo.
Ali Ibrahim, who has worked with youth in the Malmo district of Rosengaard for 25 years, remembers Krayem.
"He grew up like any other child. Then he met some friends at school and it developed into a gang that the parents weren't able to handle," he told TV4.
The Western port city of Malmo has gained a reputation of being Sweden's roughest city due to its mixture of poverty, joblessness and immigrants. Around of a third of the city's population are immigrants, double the national average, and nearly one in three are unemployed.