At least 15 men from India's southern state of Kerala are suspected to have joined the powerful Islamic State, fear their family members.
The youths have been missing since July 8 from their home town Kasaragod.
Family members said they were informed of their children's likely attachment with the militant organisation by one of their friends.
They have written to state chief minister Pinarayi Vijayan asking him to investigate the matter.
"We are ready to take him back after proper procedure and verification by the police, otherwise…going to some foreign land to join some militant organisation… we don't need him here," said the father of one of the missing youths, Hamlin.
Two other missing youths have been identified as Hafesudheen Theke Koleth and Azees Hussain.
Islamic State has struggled to win over recruits in India, which is home to the world's third-largest Muslim population.
Indian police arrested 29 men last year for establishing bases to recruit men to the Islamist militant group. All the men were charged with conspiracy to wage war against the state.
A handful of Indians are also suspected of having travelled to Iraq and Syria to join Islamic State, where the group is fighting to install an Islamic caliphate.