Ladislaus the Posthumous because he was born at Komárom four months after his father's death. He succeeded immediately as Duke of Austria and head of the House of Habsburg, and he also became nominal King of Bohemia. But his second cousin Frederick V, ruler of Inner Austria, was chosen to succeed Albert II as King of the Romans. Wikipedia
The definitive Wikipedia entry for Ladislas The Posthumous. Wikipedia is the biggest multilingual free-content encyclopedia on the Internet. en.wikipedia.org/wiki/Ladislas_the_Posthumous