Sarah Kennedy has one overriding fear. “I never want my kids to have to live through what I have with my own parents,” the 54-year-old said. Her mother Liz, 82, and father, Colin, 85, each have advanced-stage dementia. “They have been married nearly 60 years,” she said. “It has been a very strong, loving marriage — but now they don’t really know each other.” Kennedy’s genetic inheritance means she is at increased risk of developing the disease. She is determined to do whatever she can to reduce