How come nobody in the police found the relation between Brian Moser and Dexter?

Dexter tells us that he is adopted - S1 E1 Dexter recovers the repressed memory of his mother's murder - S1 E10 Dexter is directed by the ice truck killer to a newspaper detailing their mother's death. He learns that she was involved in criminal activity that led to her death. His name is suppressed from the article. - S1 E11 It can be surmised at this point that information about Dexter's biological family would have been supressed for his own protection. It is later confirmed in the series that Harry had suppressed the information and only adopted Dexter alone, fearing that the older brother was already damaged goods.