Police confirmed to a local newspaper in Aachen, near Germany's border with Belgium and the Netherlands, that the couple had been among the victims of the attacks, but would not confirm anything about their status.
The Foreign Ministry told The Local early on Thursday afternoon that they could not rule out Germans being among those killed in the blasts.
The number of Germans injured was "in the single digits," they said, adding that all but one seriously injured person had now left the hospitals in Brussels.
Germany joins chorus of criticism
Belgian authorities have come in for sharp criticism over Tuesday's bombings at Brussels airport and a metro station in the city centre, which have so far exacted a toll of 31 dead and around 300 wounded.
Of the injured, 61 are in intensive care, the Belgian Ministry of Health said in a statement. It is feared that some of those most badly hurt may succumb to their injuries.
Several Germans are believed to be among the people hurt in the attacks.
"We must address clearly the failings of the Belgian security services," Germany's EU Commissioner Günther Oettinger told Bild on Thursday.
"In Brussels alone, there are several different police authorities that don't co-operate sufficiently. Things can't stay like this."
France's Finance Minister, meanwhile, stoked tensions with the Belgians after criticizing their "naivety" over Islamist extremism in their capital.
Turkish President Recep Tayyip Erdogan said on Wednesday that one of the three suspects in the bombings had been deported from his country in June and that Belgian authorities had been informed.
Meanwhile, Israeli newspaper Haaretz reported that there had been concrete tip-offs about a possible attack in Brussels before the attacks.
On the trail of the bombers
Some progress had been made by police, who now believe they have identified all three men who blew themselves up in the suicide attacks.
All three were born in Belgium and had connections to the Islamist organizers of the Paris attacks in November.
Two of the men, Ibrahim and Khalid Al-Bakraoui, were brothers. The third man, Najim Laachraoui, had been added to wanted lists in connection with the Paris attacks shortly before the explosions in Brussels.
Interior ministers from across the EU, including Germany's Thomas de Maizière, will gather in Brussels on Thursday for an extraordinary session.
EU Commission President Jean-Claude Juncker said that proposals for boosting security in Europe had been in discussion for months following a similar meeting after the Paris attacks.