The carrier bought 45 per cent of Brussels Airlines owner SN Airholding in 2009 for €65m (£56m), with the option of buying the other 55 per cent from 2011 onwards.
Lufthansa is trying to boost its Eurowings business with acquisitions, and said earlier this year that it was discussing how to bring Brussels, which has a fleet of 49 planes, into its low-cost platform, which currently has around 90 planes.
The transaction, which is subject to shareholders of SN Airholding approving the details of the deal, is expected to be concluded at the beginning of 2017, Lufthansa said.
The supervisory board is also expected to discuss plans for Lufthansa to take on more jets for Eurowings from Air Berlin , sources told Reuters, to help make Eurowings the third largest low cost-carrier in Europe behind Ryanair and easyJet.
Lufthansa has been stepping up its bids to outperform the competition over the last year - in October 2015 the airline signed a 10-year deal with satellite communications company Inmarsat to provide high-speed internet on planes mid-air.