The incident took place on Thursday at Lahore's Allama Iqbal International Airport, Dawn news reported.
Yousuf and Abdul Aziz Abbas, sons of the late Abbas Sharif, Nawaz Sharif's younger brother, were offloaded by officials of the Federal Investigation Agency (FIA) who said their names were on the Provisional National Identity List (PNIL).
The PNIL is a new Exit Control List (ECL)-like category introduced recently in immigration laws under which a passenger can be stopped from leaving the country on the request of a government department.
Both brothers have been named in the Chaudhry Sugar Mills (CSM) case by the Lahore office of the NAB.
"NAB had recently written to the Interior Ministry to place the names of Yousuf Abbas and Abdul Aziz Abbas on the PNIL so that they could not leave the country," an FIA official told Dawn news.
He said the two brothers were shareholders in the CSM and had failed to reply to the NAB's queries regarding investments and remittances they received when they appeared recently before a combined investigation team of NAB Lahore.
"Both are facing money laundering and 'income beyond means' investigations in this case along with Nawaz Sharif, Shahbaz Sharif, Maryam Nawaz, Hamza Shahbaz and others," the official added.
( With inputs from IANS )