Complex sentence: Ann-Margret has no children, but she was stepmother to the three children of Roger Smith, an actor who later became her manager, to whom she was married from May 8,1967 until his death on June 4,2017.
Split into simpler sentences: Ann-Margret has no children, but she was stepmother to the three children of husband Roger Smith, an actor who later became her manager. She and Smith were married from May 8,1967 until his death on June 4,2017.