Serhiy Klyuev, a tycoon whose wealth from metals and property was put at around $323 million by Forbes two years ago, denied any guilt in remarks to parliament and said the charges had arisen from political pressure.
His brother, Andriy, also an oligarch, was Yanukovich's chief-of-staff and fled with his boss to Russia in the face of violent pro-Europe street protests in February 2014.
Ukrainian media say that the brothers acted as middlemen in helping Yanukovich secure a 350-acre (140-hectare) estate at Mezhihirye outside Kiev where he led a luxurious lifestyle with a palatial mansion, riverside yacht pier, hunting grounds and a menagerie of ostriches.
Acting state prosecutor Volodymyr Huzyr told parliament that Klyuev, 45, had committed "large-scale" embezzlement but did not elaborate on early charges by the prosecutor's office.
Klyuev, who has been a parliamentary deputy for the Opposition Bloc grouping many former supporters and allies of Yanukovich, said: "Investigators have not established any proof of my guilt, but the prosecutor's office has ignored this because of political pressure."
The Moscow-supported Yanukovich himself is wanted by Ukraine to face charges of being behind the shootings of protesters and of involvement in large-scale embezzlement.
Interpol has also put Yanukovich on its wanted list.
He sparked mass unrest when he announced a policy U-turn away from a course of European integration back to the Russian orbit.
After Yanukovich fell, Russia annexed Crimea and threw its support behind a rebellion by pro-Moscow separatists in Ukraine's east, sparking the biggest crisis between Russia and the West since the Cold War.
Source: Yahoo News