Claim: There are four FoxO family members in humans,  FOXO1, FOXO4, FOXO6, and FOXO3, which belong to the O subclass of the forkhead family of transcription factors which are characterized by a distinct fork head DNA-binding domain.
Evidence: FOXO3 belongs to the O subclass of the forkhead family of transcription factors which are characterized by a distinct fork head DNA-binding domain. There are three other FoxO family members in humans, FOXO1, FOXO4 and FOXO6.