Jewish Hospital & St. Mary's HealthCare in Louisville and Lexington-based Saint Joseph Health System announced Friday that the health care groups would merge to create Kentucky's largest health system. The partnership is retroactive to Jan. 1. It was initially to have included University of Louisville Hospital, but Gov. Steve Beshear denied that request last week, calling the hospital a public asset that should not be controlled by the private sector. The new umbrella organization will be known as KentuckyOne Health, although each hospital will retain its current name.