The trio were sentenced by district mahila court judge Thirunavukkarasu under Protection of Children from Sexual Offences Act.
The judge also awarded 10 years rigorous imprisonment to them. Both the sentences would run concurrently.
According to prosecution, the three along with a minor boy kidnapped the girl and took her to Karnataka in December 2012 and sexually assaulted her.
However, the girl managed to return a few days later and informed about the incident to her parents, who lodged a police complaint.