These kinds of dreams do happen when there is pre-existing OCD
already in a person. You know that this person has been a bane to the family.
In OCD, small things make big difference. Very little thoughts or incidents can trigger off big life events.
You should stop thinking about this person and avoid contact with him. Please try and divert your mind to effective and positive thinking. You may also speak to your treating psychiatrist
about changing the dose of the medicines if required.
Hope this helps.