Alright, so amongst starters, you have a few you can use to show you'll have evidence:
According to text
According to the passage
According to the information provided
As the information shows
As the text mentioned, (include direct quote here)
Based on the information in the passage/text, (include reasoning here)
Etc. There are quite a few options, really, these are just a few. Based on whatever you are providing the information ON, the words information, text, and passage can be changed to suit your needs, such as article, newspaper, website, etc.
Explanation:
Don John spoiled the wedding because he was bitter and wanted to make his brother look bad. He was the illegitimate brother, you see. Don Pedro was the legitimate brother.