The court has also ordered the state to bear the cost of raising the child born as a result of the rape.
Additional District and Sessions Judge Md Saidur Rahman Gazi announced the verdict on Thursday.
The convicts have also been fined by Tk 10,000 each. They will have to serve an additional six months in prison if they fail to pay the fine.
Convicts Main Uddin and his sister-in-law Halima Begum were on the docks when the verdict was announced.
On the night of Apr 4, 2005, Main Uddin raped a young woman with the help of Halima, claiming to be interested in marrying her, said the plaintiff’s lawyer Abul Bashar.
Police submitted the chargesheet in the case on Nov 21.
According to Bashar, Main Uddin and the mother are to be considered the legal parents of the child.
The court said the state will pay for the child’s upbringing, he said.
“The Lakshmipur district administration has been ordered, on behalf of the state, to take necessary measures.”