Billy and Miriam Locane are the two kids mentioned in the article found in the trash in Silent Hill 3.

Walter Sullivan was the man that was mentioned in a newspaper article in Silent Hill 2. The article stated that he killed Billy and Miriam Locane with an axe, and later stabbed himself in the neck with a soup spoon when they took him to jail. The spoon was found buried two inches in his neck and he was dead from blood loss.

Keep looking at the picture of Toluca Lake above Henry's couch. Examine it and at one point he should mention the superintendent telling him that his son and daughter-in-law went missing in Silent Hill a few years ago. The superintendent's surname is Sunderland, and he is most likely talking about James Sunderland, the main character of Silent Hill 2.