In my current work-in-progress, I'm touching on the issue of domestic abuse. I have a seven-year-old boy whose foster parents are alternatively hurtful and affectionate at different times. It's because the boy reminds them of the son they lost in an accident that they were partly responsible for. They are affectionate towards him because whenever they see him, they see their son, but when he is unable to live up to the image they want him to be, they hurt him.

My question is: is that realistic? Also, what are some additional "triggers" that would cause them to behave that way?

Thanks in advance!