Mohamed Abdeslam, who spoke to French TV BFM Tuesday, says his brother was devout but showed no signs of being a radical Islamist.
Abdeslam said: "Of course I call on him to turn himself over to the police. The best would be for him to give himself up so that justice can shed all the light on this."
Abdeslam added: "We think of him and we wonder where he is."
Mohamed was arrested and questioned following the attack and was released Monday. He says his brother prayed and attended a mosque occasionally but dressed in jeans and pullovers and showed no signs of being a radical.
Meanwhile, French officials told the Associated Press that they are seeking a second fugitive directly involved in the Paris attacks.
Three officials, who spoke on condition of anonymity because they were not authorized to provide details about the ongoing investigation, said an analysis of the series of attacks on Nov. 13 indicated that one person directly involved was unaccounted for.
France made an unprecedented demand Tuesday that its European Union allies support its military action against the Islamic State of Iraq and Syria (ISIS) after the attacks in Paris - a request that came as France launched new airstrikes on the militants' stronghold in Syria.
The deadly Paris attacks have galvanized international determination to confront the militants. Russian President Vladimir Putin ordered the Russian missile cruiser Moskva, currently in the Mediterranean, to start cooperating with the French military on operations in Syria and U.S. Secretary of State John Kerry suggested that a cease-fire between Syria's government and the opposition could be arranged in the next few weeks to let nations focus on fighting ISIS.
ISIS has claimed responsibility for the attacks Friday in Paris that killed at least 129 people and left over 350 wounded.
The French government invoked a never-before-used article of the EU's Lisbon Treaty obliging members of the 28-nation bloc to give "aid and assistance by all the means in their power" to a member country that is "the victim of armed aggression on its territory."
French Defense Minister Jean-Yves Le Drian said all 27 of France's EU partners responded positively, and they could help "either by taking part in France's operations in Syria or Iraq, or by easing the load or providing support for France in other operations."
"Every country said: I am going to assist, I am going to help," Drian said.
Arriving for talks in Brussels with his EU counterparts, Greek Defense Minister Panagiotis Kammenos told reporters that the Paris attacks were a game-changer for the bloc.
"This is Sept. 11 for Europe," he said.
Paris police said 16 people had been arrested in the region in relation to the deadly attacks, and police have carried out 104 raids since a state of emergency was declared Saturday.
French military spokesman Col. Gilles Jaron said the latest airstrikes in the Islamic State group's de-facto capital in the Syrian city of Raqqa destroyed a command post and training camp.
French President Francois Hollande has vowed to forge a united coalition capable of defeating the jihadists at home and abroad. NATO allies were sharing intelligence and working closely with France, NATO chief Jens Stoltenberg said.
Noting that victims of the Paris attacks came from at least 19 nations, Hollande says the international community, led by the U.S. and Russia, must overcome their deep-seated divisions over Syria to destroy ISIS on its home turf.
"(Syria is) the biggest factory of terrorism the world has ever known and the international community is still too divided and too incoherent" in its response, Hollande said, adding that the "acts of war" in Paris were decided upon and planned in Syria.
Hollande is going to visit Washington and Moscow later this month to meet with President Barack Obama and Putin to discuss ways of stepping up international cooperation against IS and how to end the fighting in Syria.
Putin's cooperation order came as Russia's defense minister said its warplanes fired cruise missiles on militant positions in Syria's Idlib and Aleppo provinces. ISIS has positions in Aleppo province, while the Nusra militant group is in Idlib. Russian bombers hit ISIS positions in Raqqa and Der-ez-Zor.
Moscow has vowed to hunt down those responsible for blowing up a Russian passenger plane over Egypt last month, killing 224 people, mostly Russian tourists. ISIS has claimed responsibility for the Oct. 31 attack.
An international police manhunt continued for the Paris attacks fugitives, including key suspect Salah Abdeslam, whose brother Brahim Abdeslam died in Friday's attacks.
Seven of the Paris attackers died Friday - six after detonating suicide belts and a seventh from police gunfire - but Iraqi intelligence officials told The Associated Press that their sources indicated 19 people had participated in the Paris attacks and five others had provided hands-on logistical support.
Two men arrested in Belgium admitted driving to France to pick up Salah Abdeslam early Saturday, their lawyers said.
Mohammed Amri, 27, denies any involvement in the attacks and says he went to Paris to collect his friend Salah Abdeslam, according to his defense lawyer Xavier Carrette. Hamza Attou, 21, says he went along to keep Amri company, his lawyer Carine Couquelet said. Both are being held on charges of terrorist murder and conspiracy.
Belgian media reported that Amri and Attou were being investigated as potential suppliers of the suicide bombs used in the attacks, since ammonium nitrate, a fertilizer that can be used to make explosives, was discovered in a search of their residence.
The defense lawyers said they could not confirm those reports.
Salah Abdeslam and his brother booked a hotel in the southeastern Paris suburb of Alfortville and rented a house in the northeastern suburb of Bobigny several days before the attacks, a French judicial official told The Associated Press. She spoke on condition of anonymity because she was not authorized to speak about the ongoing investigation.
On Tuesday, German police said three foreigners with possible links to the Paris attacks were arrested by a SWAT team near the western city of Aachen, close to the border with Belgium. Local media said two women and one man were arrested as they left a job center.
Another Belgian car with a shattered front passenger window was found Tuesday in northern Paris - officials said it was the third vehicle identified as having possible links to the attacks investigation.
Belgium is deploying 300 extra soldiers to help provide security in major cities.
Kerry flew to France as a gesture of solidarity and met Hollande and Foreign Minister Laurent Fabius on Tuesday.
A cease-fire between Syria's government and the opposition - which would allow nations supporting Syria's various factions to focus more on IS - could be just weeks away, Kerry said, describing it as potentially a "gigantic step," opening the way for deeper international cooperation.
Standing next to Hollande at the Elysee Palace, Kerry said the carnage in the French capital, along with recent attacks in Egypt, Lebanon and Turkey, made it clear that more pressure must be brought to bear on ISIS extremists.
A U.S intelligence source told CBS News that U.S. intelligence has identified Abdelhamid Abaaoud as the "mastermind" of the Paris terror plot and the key ISIS operative "for external operations in Europe and is operating in Syria."
One official cited chatter from ISIS figures that Abaaoud had recommended a concert as an ideal target for inflicting maximum casualties, as well as electronic communications between Abaaoud and one of the Paris attackers who blew himself up. The official spoke on condition of anonymity to discuss the sensitive investigation.
Abaaoud came to public attention last year by boasting in an ISIS propaganda video about his pride in piling the dead bodies of "infidel" enemies into a trailer. He has been linked to a failed terrorist plot in Belgium and an attempt to gun down passengers on a high-speed train to Paris that was foiled by three Americans.
Still, French Interior Minister Bernard Cazeneuve conceded that "the majority of those who were involved in this attack (in Paris) were unknown to our services."
In Paris, the Eiffel Tower shut down again Tuesday, after opening for just a day, and heavily armed troops patrolled the courtyard of the Louvre Museum.
In a show of solidarity, British Prime Minister David Cameron was to join Prince William at a friendly soccer match Tuesday night between England and France in London's Wembley Stadium. Armed police were patrolling the site and British fans, in a show of solidarity, were being encouraged to sing the French national anthem as well.