Natore District and Sessions' Judge Rezaul Karim passed the order on Wednesday and fined them Tk10,000 each for murdering Yasin Arafat alias Emon.
The convicts are Emdadul Hoque Milon, 37, of Kamardah village under Baraigram upazila, and his wife Nahida Begum, 24 who remains on the run.
Milon divorced Emon's mother and married off Nahida later.
According to the case statement, Milon and Nahida had strangled Emon to death on August 27, 2015.
In the incident, Emon's mother Kulsuma Begum lodged a murder case against the duo with Baraigram police station and the court came up with the verdict after examining evidence and witness.
Kulsuma Begum claimed that Milon is a highway robber and their separation took place as she protested his crimes.