Here's how the relationship works:

In 1931, Goebbels married Magda Quandt, who'd previously been married to industrialist Guenther Quandt (as well as another man before). Harald Quandt (actually the son of Magda's first husband) wound up living with Goebbels after the marriage. When Guenther — himself implicated as a Nazi follower though not involved in the regime’s crimes — died, Harald and his half-brother Herbert Quandt inherited his fortune.

That included ownership of two large manufacturing firms as well as stakes in Daimler-Benz and potash miner Wintershall AG.