Do you remember when the dream started when you were a kid? Maybe you did something or something happened that set it off. I think, since it started back then, you'd have to think about what you felt about farms and the other images back then? I remember my first readers in school and the characters went to the farm and that influences my thinking about "farms" even today; or, if you saw any scary movies with ax murderers :-) etc. Maybe you heard the Lizzie Borden rhyme, for example and it went places in your imagination you weren't aware of. It does seem like a "basic" dream, maybe you were angry and wished your parents/siblings dead and/or it just became a habit that when you get angry, you have this dream instead of learning to deal with your emotions better?