Radu was the only son of Nicholas Alexander of Wallachia by his second wife, Clara Dobokai. He was co-ruler with his half-brother Vladislav I at least from 1372. He may have started his reign as sole ruler after 9 July 1374 when the last documentary mention of his brother as being alive is dated. Unfortunately, there aren't any internal documents that could attest his reign. There are a few external mentions of him, primarily documents of the Kingdom of Hungary and a contemporary Italian chronicle and also a late pisanie, an inscription on the walls of Curtea de Argeș Cathedral and an important quantity of coins (ducati, dinari and bani) which were emitted by the voievod .
