Will Hayward
Doctor William Hayward (played by Warren Frost) is a physician and coroner who, due to his close relationship with her, refuses to perform the autopsy on Laura Palmer. His first name is not generally used, but because he is referred to as "Will" in several episodes, it can be presumed to be "William"; he is normally referred to as just "Doc" most of the time.
He is the husband of Eileen and father of three daughters: Donna (who has by far the biggest role of the family), Harriet, and Gersten. The Doc is generally a balanced, fair man, but he is especially upset by Laura's murder, as he is a friend of the Palmer family, and his daughters knew her well.
Doc Hayward also has an altercation with the abrasive Albert Rosenfield, who calls his work "amateur", and wishes to do more work on Laura's corpse. Unlike most of the characters on Twin Peaks he appears to have no major nasty secrets, or eccentricities, and appears to be an overall moral figure. However, towards the end of the second season, we learn he may have been cuckolded by Benjamin Horne, who might in fact be Donna's real father - a question left unresolved due to the series' cancellation. In the final episode, Doc Hayward attacks Benjamin and although it seems that Ben has been seriously injured (possibly killed), Doc Hayward shows up at the end of the episode relatively back to his normal temperament.
Read more about this topic: Lil The Dancer, Hayward Family