 John Corvinus was the illegitimate son of King Matthias and his mistress , Barbara <unk> . John Corvinus was born on 2 April 1473 . Matthias recognized in public that John is his son and granted him the title of Duke of <unk> ( present @-@ day <unk> , Slovakia ) in 1481 . John Corvinus received a number of land grants from his father in the subsequent years . King Matthias granted him the Duchy of Troppau and five further Silesian duchies — <unk> , <unk> , <unk> , <unk> , and Tost — in 1485 . 
