William Reid is Dr. Spencer Reid's father and Diana Reid's husband. When Spencer is eight William walks out on the family. It is later revealed that he moved a mere nine miles away and built up a successful business. He archived every article that mentioned Spencer on his computer. He never started another family.It is later shown that William and Diana's marriage dissolved largely due to the pressures of keeping a monumental secret involving the rape and murder of a friend of Spencer's four years before his father walked out, as well as Diana's deteriorating mental condition.William does love his son and seems to want a relationship with him but Spencer is enraged by his father's abandonment.