Families that have schizophrenia also have higher rates of Schizoid and Schizotypal Personality Disorder. They believe there is really a continuum of severity in Schizophrenia, with Schizoid being very mild, Schizotypal more so and schizophrenia full blown illness. There have been no established links between bipolar and schizophrenia that I know of. Families with bipolar have more incidence of unipolar depression in other family members though, so there is a link between bipolar and unipolar depression.