Answer:
He hated his foster father because his father had multiple affairs
Step-by-step explanation:
The name of his foster father was John Allan.
Even before Edgar knew about the affair, both of them dislike one another. They're both strong headed individuals whose principles are not suitable with one another.
After Edgar knew about John's affair, his hatred toward his foster father was amplified. He blame His foster father's affair as the cause of sickness that his mother experienced