Complex sentence: He is believed to die in the year 1511 because its said that he was used to the habit of being drunk and his stepmother hated him and so one day she gave her a glass of drink with poison mixed in it.
Split into simpler sentences: He is believed to die in the year 1511 because its said that he was used to the habit of drinking. His stepmother hated him, and so one day she gave him a drink with poison mixed in it.